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With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to every cell. Each day, 2,000 gallons of blood travel many times through about 60,000 miles of blood vessels that branch and cross, linking the cells of our organs and body parts.
About the Heart and Circulatory System
The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries. Our bodies actually have two circulatory systems: The pulmonary circulation is a short loop from the heart to the lungs and back again, and the systemic circulation (the system we usually think of as our circulatory system) sends blood from the heart to all the other parts of our bodies and back again.
The heart is the key organ in the circulatory system. As a hollow, muscular pump, its main function is to propel blood throughout the body. It usually beats from 60 to 100 times per minute, but can go much faster when necessary. It beats about 100,000 times a day, more than 30 million times per year, and about 2.5 billion times in a 70-year lifetime.
The heart gets messages from the body that tell it when to pump more or less blood depending on an individual's needs. When we're sleeping, it pumps just enough to provide for the lower amounts of oxygen needed by our bodies at rest. When we're exercising or frightened, the heart pumps faster to increase the delivery of oxygen.
The heart has four chambers that are enclosed by thick, muscular walls. It lies between the lungs and just to the left of the middle of the chest cavity. The bottom part of the heart is divided into two chambers called the right and left ventricles, which pump blood out of the heart. A wall called the interventricular septum divides the ventricles.
The upper part of the heart is made up of the other two chambers of the heart, the right and left atria. The right and left atria receive the blood entering the heart. A wall called the interatrial septum divides the right and left atria, which are separated from the ventricles by the atrioventricular valves. The tricuspid valve separates the right atrium from the right ventricle, and the mitral valve separates the left atrium and the left ventricle.
Two other cardiac valves separate the ventricles and the large blood vessels that carry blood leaving the heart. These are the pulmonic valve, which separates the right ventricle from the pulmonary artery leading to the lungs, and the aortic valve, which separates the left ventricle from the aorta, the body's largest blood vessel.
Arteries carry blood away from the heart. They are the thickest blood vessels, with muscular walls that contract to keep the blood moving away from the heart and through the body. In the systemic circulation, oxygen-rich blood is pumped from the heart into the aorta. This huge artery curves up and back from the left ventricle, then heads down in front of the spinal column into the abdomen. Two coronary arteries branch off at the beginning of the aorta and divide into a network of smaller arteries that provide oxygen and nourishment to the muscles of the heart.
Unlike the aorta, the body's other main artery, the pulmonary artery, carries oxygen-poor blood. From the right ventricle, the pulmonary artery divides into right and left branches, on the way to the lungs where blood picks up oxygen.
Arterial walls have three layers:
1. The endothelium is on the inside and provides a smooth lining for blood to flow over as it moves through the artery.
2. The media is the middle part of the artery, made up of a layer of muscle and elastic tissue.
3. The adventitia is the tough covering that protects the outside of the artery.
As they get farther from the heart, the arteries branch out into arterioles, which are smaller and less elastic.
Veins carry blood back to the heart. They're not as muscular as arteries, but they contain valves that prevent blood from flowing backward. Veins have the same three layers that arteries do, but are thinner and less flexible. The two largest veins are the superior and inferior vena cavae. The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.
A network of tiny capillaries connects the arteries and veins. Though tiny, the capillaries are one of the most important parts of the circulatory system because it's through them that nutrients and oxygen are delivered to the cells. In addition, waste products such as carbon dioxide are also removed by the capillaries.
What the Heart and Circulatory System Do
The circulatory system works closely with other systems in our bodies. It supplies oxygen and nutrients to our bodies by working with the respiratory system. At the same time, the circulatory system helps carry waste and carbon dioxide out of the body.
Hormones — produced by the endocrine system — are also transported through the blood in the circulatory system. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. For example, one of the hormones produced by the heart helps control the kidneys' release of salt from the body.
One complete heartbeat makes up a cardiac cycle, which consists of two phases:
1. In the first phase, the ventricles contract (this is called systole), sending blood into the pulmonary and systemic circulation. To prevent the flow of blood backwards into the atria during systole, the atrioventricular valves close, creating the first sound (the lub). When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. This is what creates the second sound (the dub).
2. Then the ventricles relax (this is called diastole) and fill with blood from the atria, which makes up the second phase of the cardiac cycle.
A unique electrical conduction system in the heart causes it to beat in its regular rhythm. The sinoatrial or SA node, a small area of tissue in the wall of the right atrium, sends out an electrical signal to start the contracting of the heart muscle. This node is called the pacemaker of the heart because it sets the rate of the heartbeat and causes the rest of the heart to contract in its rhythm.
These electrical impulses cause the atria to contract first, and then travel down to the atrioventricular or AV node, which acts as a kind of relay station. From here the electrical signal travels through the right and left ventricles, causing them to contract and forcing blood out into the major arteries.
In the systemic circulation, blood travels out of the left ventricle, to the aorta, to every organ and tissue in the body, and then back to the right atrium. The arteries, capillaries, and veins of the systemic circulatory system are the channels through which this long journey takes place.
Once in the arteries, blood flows to smaller arterioles and then to capillaries. While in the capillaries, the bloodstream delivers oxygen and nutrients to the body's cells and picks up waste materials. Blood then goes back through the capillaries into venules, and then to larger veins until it reaches the vena cavae.
Blood from the head and arms returns to the heart through the superior vena cava, and blood from the lower parts of the body returns through the inferior vena cava. Both vena cavae deliver this oxygen-depleted blood into the right atrium. From here the blood exits to fill the right ventricle, ready to be pumped into the pulmonary circulation for more oxygen.
In the pulmonary circulation, blood low in oxygen but high in carbon dioxide is pumped out the right ventricle into the pulmonary artery, which branches off in two directions. The right branch goes to the right lung, and vice versa.
In the lungs, the branches divide further into capillaries. Blood flows more slowly through these tiny vessels, allowing time for gases to be exchanged between the capillary walls and the millions of alveoli, the tiny air sacs in the lungs.
During the process called oxygenation, oxygen is taken up by the bloodstream. Oxygen locks onto a molecule called hemoglobin in the red blood cells. The newly oxygenated blood leaves the lungs through the pulmonary veins and heads back to the heart. It enters the heart in the left atrium, then fills the left ventricle so it can be pumped into the systemic circulation.
Problems of the Heart and Circulatory System
Problems with the cardiovascular system are common — more than 64 million Americans have some type of cardiac problem. But cardiovascular problems don't just affect older people — many heart and circulatory system problems affect children and teens, too.
Heart and circulatory problems are grouped into two categories: congenital (problems present at birth) and acquired (problems developed some time after birth).
Congenital heart defects. These abnormalities in the heart's structure are present at birth. Approximately 8 out of every 1,000 newborns have congenital heart defects ranging from mild to severe. These defects occur while the fetus is developing in the mother's uterus and it's not usually known why they occur. Some congenital heart defects are caused by genetic disorders, but most are not. What all congenital heart defects have in common, however, is that they involve abnormal or incomplete development of the heart.
A common sign of a congenital heart defect is a heart murmur — an abnormal sound (like a blowing or whooshing sound) that's heard when listening to the heart. Usually a heart murmur is detected by a doctor who's listening to the heart with a stethoscope during a routine exam. Murmurs are very common in children and can be caused by congenital heart defects or other heart conditions.
Arrhythmia. Cardiac arrhythmias, also called dysrhythmias or rhythm disorders, are problems in the rhythm of the heartbeat. They may be caused by a congenital heart defect or they may be acquired later. An arrhythmia may cause the heart's rhythm to be irregular, abnormally fast, or abnormally slow. Arrhythmias can occur at any age and may be discovered during a routine physical examination. Depending on the type of rhythm disorder, an arrhythmia may be treated with medication, surgery, or pacemakers.
Cardiomyopathy. This chronic disease causes the heart muscle (the myocardium) to become weakened. Usually, it first affects the lower chambers of the heart, the ventricles, and then progresses and damages the muscle cells and even the tissues surrounding the heart. In its most severe forms, it can lead to heart failure and even death. Cardiomyopathy is the #1 reason for heart transplants in children.
Coronary artery disease. The most common heart disorder in adults, coronary artery disease is caused by atherosclerosis. Deposits of fat, calcium, and dead cells, called atherosclerotic plaques, form on the inner walls of the coronary arteries (the blood vessels that supply the heart) and interfere with the smooth flow of blood. Blood flow to the heart muscle may even stop if a thrombus, or clot, forms in a coronary vessel, which may cause a heart attack. In a heart attack (or myocardial infarction), the heart muscle becomes damaged by lack of oxygen, and unless blood flow returns within minutes, muscle damage increases and the heart's ability to pump blood is compromised. If the clot can be dissolved within a few hours, damage to the heart can be reduced. Heart attacks are rare in kids and teens.
Hypercholesterolemia (high cholesterol). Cholesterol is a waxy substance that's found in the body's cells, in the blood, and in some foods. Having too much cholesterol in the blood, also known as hypercholesterolemia, is a major risk factor for heart disease and can lead to a heart attack.
Cholesterol is carried in the bloodstream by lipoproteins. Two kinds — low-density lipoproteins (LDL) and high-density lipoproteins (HDL) — are the most important. High levels of LDL cholesterol (the bad cholesterol) increase a person's risk for heart disease and stroke, whereas high levels of HDL cholesterol (the good cholesterol) can protect against these.
A blood test can indicate if someone's cholesterol is too high. A child's cholesterol level is borderline if it's 170 to 199 mg/dL, and it's considered high if it's above 200 mg/dL.
About 10% of teens between 12 and 19 have high cholesterol levels that put them at increased risk of cardiovascular disease.
High blood pressure (hypertension). Over time, high blood pressure can damage the heart, arteries, and other body organs. Symptoms can include headache, nosebleeds, dizziness, and lightheadedness. Infants, kids, and teens can have high blood pressure, which may be caused by genetic factors, excess body weight, diet, lack of exercise, and diseases such as heart disease or kidney disease.
Kawasaki disease. Also known as mucocutaneous lymph node syndrome, Kawasaki disease affects the mucous membranes (the lining of the mouth and breathing passages), the skin, and the lymph nodes (part of the immune system). It can also lead to vasculitis, an inflammation of the blood vessels. This can affect all major arteries in the body — including the coronary arteries. It can also cause inflammation of the heart muscle, called myocarditis. When coronary arteries become inflamed, a child can develop aneurysms, which are weakened and bulging spots on the walls of arteries. This increases the risk of a blood clot forming in this weakened area, which can block the artery, possibly leading to a heart attack. In addition to the coronary arteries, the heart muscle, lining, valves, or the outer membrane that surrounds the heart can become inflamed. Arrhythmias or abnormal functioning of some heart valves can occur. Kawasaki disease has surpassed rheumatic fever as the leading cause of acquired heart disease in children in the United States.
Rheumatic heart disease. Usually the complication of an untreated strep throat infection, rheumatic fever can lead to permanent heart damage and even death. Most common in kids between 5 and 15 years of age, it begins when antibodies the body produces to fight the strep infection begin to attack other parts of the body. They react to tissues in the heart valves as though they were the strep bacteria and cause the heart valves to thicken and scar. Inflammation and weakening of the heart muscle may also occur. Usually, when strep throat infections are promptly treated with antibiotics, this condition can be avoided.
Stroke. Strokes occur when the blood supply to the brain is cut off or when a blood vessel in the brain bursts and spills blood into an area of the brain, causing damage to brain cells. Children or infants who have experienced stroke may be suddenly numb or weak, especially on one side of the body, and they may experience a sudden severe headache, nausea or vomiting, and difficulty seeing, speaking, walking, or moving. During childhood, strokes are rare.
Getting plenty of exercise, eating a nutritious diet, maintaining a healthy weight, and getting regular medical checkups are the best ways to help keep the heart healthy and avoid long-term problems like high blood pressure, high cholesterol, and heart disease.
"I pray that this article empowers you to Get A L.I.F.E."
Friday, May 27, 2011
Saturday, May 21, 2011
The Female Reproductive System
About Human Reproduction
All living things reproduce. Reproduction — the process by which organisms make more organisms like themselves — is one of the things that sets living things apart from nonliving matter. But even though the reproductive system is essential to keeping a species alive, unlike other body systems, it's not essential to keeping an individual alive.
In the human reproductive process, two kinds of sex cells, or gametes, are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female's reproductive system to create a new individual.
Both the male and female reproductive systems are essential for reproduction. The female needs a male to fertilize her egg, even though it is she who carries offspring through pregnancy and childbirth.
Humans, like other organisms, pass certain characteristics of themselves to the next generation through their genes, the special carriers of human traits. The genes that parents pass along are what make their children similar to others in their family, but also what make each child unique. These genes come from the male's sperm and the female's egg.
Most species have two sexes: male and female. Each sex has its own unique reproductive system. They are different in shape and structure, but both are specifically designed to produce, nourish, and transport either the egg or sperm.
Components of the Female Reproductive System
Unlike the male, the human female has a reproductive system located entirely in the pelvis. The external part of the female reproductive organs is called the vulva, which means covering. Located between the legs, the vulva covers the opening to the vagina and other reproductive organs located inside the body.
The fleshy area located just above the top of the vaginal opening is called the mons pubis. Two pairs of skin flaps called the labia (which means lips) surround the vaginal opening. The clitoris, a small sensory organ, is located toward the front of the vulva where the folds of the labia join. Between the labia are openings to the urethra (the canal that carries urine from the bladder to the outside of the body) and vagina. Once girls become sexually mature, the outer labia and the mons pubis are covered by pubic hair.
A female's internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.
The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. The vagina is about 3 to 5 inches (8 to 12 centimeters) long in a grown woman. Because it has muscular walls, it can expand and contract. This ability to become wider or narrower allows the vagina to accommodate something as slim as a tampon and as wide as a baby. The vagina's muscular walls are lined with mucous membranes, which keep it protected and moist.
The vagina serves three purposes:
1. It's where the penis is inserted during sexual intercourse.
2. It's the pathway that a baby takes out of a woman's body during childbirth, called the birth canal.
3. It provides the route for the menstrual blood (the period) to leave the body from the uterus.
A thin sheet of tissue with one or more holes in it called the hymen partially covers the opening of the vagina. Hymens are often different from female to female. Most women find their hymens have stretched or torn after their first sexual experience, and the hymen may bleed a little (this usually causes little, if any, pain). Some women who have had sex don't have much of a change in their hymens, though.
The vagina connects with the uterus, or womb, at the cervix (which means neck). The cervix has strong, thick walls. The opening of the cervix is very small (no wider than a straw), which is why a tampon can never get lost inside a girl's body. During childbirth, the cervix can expand to allow a baby to pass.
The uterus is shaped like an upside-down pear, with a thick lining and muscular walls — in fact, the uterus contains some of the strongest muscles in the female body. These muscles are able to expand and contract to accommodate a growing fetus and then help push the baby out during labor. When a woman isn't pregnant, the uterus is only about 3 inches (7.5 centimeters) long and 2 inches (5 centimeters) wide.
At the upper corners of the uterus, the fallopian tubes connect the uterus to the ovaries. The ovaries are two oval-shaped organs that lie to the upper right and left of the uterus. They produce, store, and release eggs into the fallopian tubes in the process called ovulation. Each ovary measures about 1½ to 2 inches (4 to 5 centimeters) in a grown woman.
There are two fallopian tubes, each attached to a side of the uterus. The fallopian tubes are about 4 inches (10 centimeters) long and about as wide as a piece of spaghetti. Within each tube is a tiny passageway no wider than a sewing needle. At the other end of each fallopian tube is a fringed area that looks like a funnel. This fringed area wraps around the ovary but doesn't completely attach to it. When an egg pops out of an ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube's lining help push it down the narrow passageway toward the uterus.
The ovaries are also part of the endocrine system because they produce female sex hormones such as estrogen and progesterone.
What the Female Reproductive System Does
The female reproductive system enables a woman to:
produce eggs (ova)
have sexual intercourse
protect and nourish the fertilized egg until it is fully developed
give birth
Sexual reproduction couldn't happen without the sexual organs called the gonads. Although most people think of the gonads as the male testicles, both sexes actually have gonads: In females the gonads are the ovaries. The female gonads produce female gametes (eggs); the male gonads produce male gametes (sperm). After an egg is fertilized by the sperm, the fertilized egg is called the zygote.
When a baby girl is born, her ovaries contain hundreds of thousands of eggs, which remain inactive until puberty begins. At puberty, the pituitary gland, located in the central part of the brain, starts making hormones that stimulate the ovaries to produce female sex hormones, including estrogen. The secretion of these hormones causes a girl to develop into a sexually mature woman.
Toward the end of puberty, girls begin to release eggs as part of a monthly period called the menstrual cycle. Approximately once a month, during ovulation, an ovary sends a tiny egg into one of the fallopian tubes.
Unless the egg is fertilized by a sperm while in the fallopian tube, the egg dries up and leaves the body about 2 weeks later through the uterus — this is menstruation. Blood and tissues from the inner lining of the uterus combine to form the menstrual flow, which in most girls lasts from 3 to 5 days. A girl's first period is called menarche.
It's common for women and girls to experience some discomfort in the days leading to their periods. Premenstrual syndrome (PMS) includes both physical and emotional symptoms that many girls and women get right before their periods, such as acne, bloating, fatigue, backaches, sore breasts, headaches, constipation, diarrhea, food cravings, depression, irritability, or difficulty concentrating or handling stress. PMS is usually at its worst during the 7 days before a girl's period starts and disappears once it begins.
Many girls also experience abdominal cramps during the first few days of their periods caused by prostaglandins, chemicals in the body that make the smooth muscle in the uterus contract. These involuntary contractions can be either dull or sharp and intense.
It can take up to 2 years from menarche for a girl's body to develop a regular menstrual cycle. During that time, her body is adjusting to the hormones puberty brings. On average, the monthly cycle for an adult woman is 28 days, but the range is from 23 to 35 days.
Fertilization
If a female and male have sex within several days of the female's ovulation, fertilization can occur. When the male ejaculates (when semen leaves a male's penis), between 0.05 and 0.2 fluid ounces (1.5 to 6.0 milliliters) of semen is deposited into the vagina. Between 75 and 900 million sperm are in this small amount of semen, and they "swim" up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. It takes only one sperm to fertilize the egg.
About a week after the sperm fertilizes the egg, the fertilized egg (zygote) has become a multicelled blastocyst. A blastocyst is about the size of a pinhead, and it's a hollow ball of cells with fluid inside. The blastocyst burrows itself into the lining of the uterus, called the endometrium. The hormone estrogen causes the endometrium to become thick and rich with blood. Progesterone, another hormone released by the ovaries, keeps the endometrium thick with blood so that the blastocyst can attach to the uterus and absorb nutrients from it. This process is called implantation.
As cells from the blastocyst take in nourishment, another stage of development, the embryonic stage, begins. The inner cells form a flattened circular shape called the embryonic disk, which will develop into a baby. The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo.
After approximately 8 weeks, the embryo is about the size of an adult's thumb, but almost all of its parts — the brain and nerves, the heart and blood, the stomach and intestines, and the muscles and skin — have formed.
During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus floats in amniotic fluid inside the amniotic sac. The fetus receives oxygen and nourishment from the mother's blood via the placenta, a disk-like structure that sticks to the inner lining of the uterus and connects to the fetus via the umbilical cord. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother's body.
Pregnancy lasts an average of 280 days — about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. The mucus that has formed a plug in the cervix loosens, and with amniotic fluid, comes out through the vagina when the mother's water breaks.
When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin. The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The baby's head usually comes first; the umbilical cord comes out with the baby and is cut after the baby is delivered.
The last stage of the birth process involves the delivery of the placenta, which at that point is called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.
Problems of the Female Reproductive System
Some girls might experience reproductive system problems, such as:
Problems of the Vulva and Vagina
Vulvovaginitis is an inflammation of the vulva and vagina. It may be caused by irritating substances (such as laundry soaps or bubble baths) or poor personal hygiene (such as wiping from back to front after a bowel movement). Symptoms include redness and itching in the vaginal and vulvar areas and sometimes vaginal discharge. Vulvovaginitis also can be caused by an overgrowth of Candida, a fungus normally present in the vagina.
Nonmenstrual vaginal bleeding is most commonly due to the presence of a vaginal foreign body, often wadded-up toilet paper. It may also be due to urethral prolapse, in which the mucous membranes of the urethra protrude into the vagina and form a tiny, doughnut-shaped mass of tissue that bleeds easily. It also can be due to a straddle injury (such as when falling onto a gymnastics beam or bicycle frame) or vaginal trauma from sexual abuse.
Labial adhesions, the sticking together or adherence of the labia in the midline, usually appear in infants and young girls. Although there are usually no symptoms associated with this condition, labial adhesions can lead to an increased risk of urinary tract infection. Sometimes topical estrogen cream is used to help separate the labia.
Problems of the Ovaries and Fallopian Tubes
Ectopic pregnancy occurs when a fertilized egg, or zygote, doesn't travel into the uterus, but instead grows rapidly in the fallopian tube. A woman with this condition can develop severe abdominal pain and should see a doctor because surgery may be necessary.
Endometriosis occurs when tissue normally found only in the uterus starts to grow outside the uterus — in the ovaries, fallopian tubes, or other parts of the pelvic cavity. It can cause abnormal bleeding, painful periods, and general pelvic pain.
Ovarian tumors, although they're rare, can occur. Girls with ovarian tumors may have abdominal pain and masses that can be felt in the abdomen. Surgery may be needed to remove the tumor.
Ovarian cysts are noncancerous sacs filled with fluid or semisolid material. Although they are common and generally harmless, they can become a problem if they grow very large. Large cysts may push on surrounding organs, causing abdominal pain. In most cases, cysts will disappear on their own and treatment is unnecessary. If the cysts are painful, a doctor may prescribe birth control pills to alter their growth or they may be removed by a surgeon.
Polycystic ovary syndrome is a hormone disorder in which too many male hormones (androgens) are produced by the ovaries. This condition causes the ovaries to become enlarged and develop many fluid-filled sacs, or cysts. It often first appears during the teen years. Depending on the type and severity of the condition, it may be treated with drugs to regulate hormone balance and menstruation.
Ovarian torsion, or the twisting of the ovary, can occur when an ovary becomes twisted because of a disease or a developmental abnormality. The torsion blocks blood from flowing through the blood vessels that supply and nourish the ovaries. The most common symptom is lower abdominal pain. Surgery is usually necessary to correct it.
Menstrual Problems
A variety of menstrual problems can affect girls, including:
Dysmenorrhea is when a girl has painful periods.
Menorrhagia is when a girl has a very heavy periods with excess bleeding.
Oligomenorrhea is when a girl misses or has infrequent periods, even though she's been menstruating for a while and isn't pregnant.
Amenorrhea is when a girl has not started her period by the time she is 16 years old or 3 years after starting puberty, has not developed signs of puberty by age 14, or has had normal periods but has stopped menstruating for some reason other than pregnancy.
Infections of the Female Reproductive System
Sexually transmitted infections (STIs). These include infections and diseases such as pelvic inflammatory disease (PID), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), human papillomavirus (HPV, or genital warts), syphilis, chlamydia, gonorrhea, and genital herpes (HSV). Most are spread from one person to another by sexual contact.
Toxic shock syndrome. This uncommon illness is caused by toxins released into the body during a type of bacterial infection that is more likely to develop if a tampon is left in too long. It can produce high fever, diarrhea, vomiting, and shock.
If you think your daughter may have symptoms of a problem with her reproductive system or if you have questions about her growth and development, talk to your doctor — many problems with the female reproductive system can be treated.
"I pray that this article empowers you to Get A L.I.F.E."
All living things reproduce. Reproduction — the process by which organisms make more organisms like themselves — is one of the things that sets living things apart from nonliving matter. But even though the reproductive system is essential to keeping a species alive, unlike other body systems, it's not essential to keeping an individual alive.
In the human reproductive process, two kinds of sex cells, or gametes, are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female's reproductive system to create a new individual.
Both the male and female reproductive systems are essential for reproduction. The female needs a male to fertilize her egg, even though it is she who carries offspring through pregnancy and childbirth.
Humans, like other organisms, pass certain characteristics of themselves to the next generation through their genes, the special carriers of human traits. The genes that parents pass along are what make their children similar to others in their family, but also what make each child unique. These genes come from the male's sperm and the female's egg.
Most species have two sexes: male and female. Each sex has its own unique reproductive system. They are different in shape and structure, but both are specifically designed to produce, nourish, and transport either the egg or sperm.
Components of the Female Reproductive System
Unlike the male, the human female has a reproductive system located entirely in the pelvis. The external part of the female reproductive organs is called the vulva, which means covering. Located between the legs, the vulva covers the opening to the vagina and other reproductive organs located inside the body.
The fleshy area located just above the top of the vaginal opening is called the mons pubis. Two pairs of skin flaps called the labia (which means lips) surround the vaginal opening. The clitoris, a small sensory organ, is located toward the front of the vulva where the folds of the labia join. Between the labia are openings to the urethra (the canal that carries urine from the bladder to the outside of the body) and vagina. Once girls become sexually mature, the outer labia and the mons pubis are covered by pubic hair.
A female's internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.
The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. The vagina is about 3 to 5 inches (8 to 12 centimeters) long in a grown woman. Because it has muscular walls, it can expand and contract. This ability to become wider or narrower allows the vagina to accommodate something as slim as a tampon and as wide as a baby. The vagina's muscular walls are lined with mucous membranes, which keep it protected and moist.
The vagina serves three purposes:
1. It's where the penis is inserted during sexual intercourse.
2. It's the pathway that a baby takes out of a woman's body during childbirth, called the birth canal.
3. It provides the route for the menstrual blood (the period) to leave the body from the uterus.
A thin sheet of tissue with one or more holes in it called the hymen partially covers the opening of the vagina. Hymens are often different from female to female. Most women find their hymens have stretched or torn after their first sexual experience, and the hymen may bleed a little (this usually causes little, if any, pain). Some women who have had sex don't have much of a change in their hymens, though.
The vagina connects with the uterus, or womb, at the cervix (which means neck). The cervix has strong, thick walls. The opening of the cervix is very small (no wider than a straw), which is why a tampon can never get lost inside a girl's body. During childbirth, the cervix can expand to allow a baby to pass.
The uterus is shaped like an upside-down pear, with a thick lining and muscular walls — in fact, the uterus contains some of the strongest muscles in the female body. These muscles are able to expand and contract to accommodate a growing fetus and then help push the baby out during labor. When a woman isn't pregnant, the uterus is only about 3 inches (7.5 centimeters) long and 2 inches (5 centimeters) wide.
At the upper corners of the uterus, the fallopian tubes connect the uterus to the ovaries. The ovaries are two oval-shaped organs that lie to the upper right and left of the uterus. They produce, store, and release eggs into the fallopian tubes in the process called ovulation. Each ovary measures about 1½ to 2 inches (4 to 5 centimeters) in a grown woman.
There are two fallopian tubes, each attached to a side of the uterus. The fallopian tubes are about 4 inches (10 centimeters) long and about as wide as a piece of spaghetti. Within each tube is a tiny passageway no wider than a sewing needle. At the other end of each fallopian tube is a fringed area that looks like a funnel. This fringed area wraps around the ovary but doesn't completely attach to it. When an egg pops out of an ovary, it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube's lining help push it down the narrow passageway toward the uterus.
The ovaries are also part of the endocrine system because they produce female sex hormones such as estrogen and progesterone.
What the Female Reproductive System Does
The female reproductive system enables a woman to:
produce eggs (ova)
have sexual intercourse
protect and nourish the fertilized egg until it is fully developed
give birth
Sexual reproduction couldn't happen without the sexual organs called the gonads. Although most people think of the gonads as the male testicles, both sexes actually have gonads: In females the gonads are the ovaries. The female gonads produce female gametes (eggs); the male gonads produce male gametes (sperm). After an egg is fertilized by the sperm, the fertilized egg is called the zygote.
When a baby girl is born, her ovaries contain hundreds of thousands of eggs, which remain inactive until puberty begins. At puberty, the pituitary gland, located in the central part of the brain, starts making hormones that stimulate the ovaries to produce female sex hormones, including estrogen. The secretion of these hormones causes a girl to develop into a sexually mature woman.
Toward the end of puberty, girls begin to release eggs as part of a monthly period called the menstrual cycle. Approximately once a month, during ovulation, an ovary sends a tiny egg into one of the fallopian tubes.
Unless the egg is fertilized by a sperm while in the fallopian tube, the egg dries up and leaves the body about 2 weeks later through the uterus — this is menstruation. Blood and tissues from the inner lining of the uterus combine to form the menstrual flow, which in most girls lasts from 3 to 5 days. A girl's first period is called menarche.
It's common for women and girls to experience some discomfort in the days leading to their periods. Premenstrual syndrome (PMS) includes both physical and emotional symptoms that many girls and women get right before their periods, such as acne, bloating, fatigue, backaches, sore breasts, headaches, constipation, diarrhea, food cravings, depression, irritability, or difficulty concentrating or handling stress. PMS is usually at its worst during the 7 days before a girl's period starts and disappears once it begins.
Many girls also experience abdominal cramps during the first few days of their periods caused by prostaglandins, chemicals in the body that make the smooth muscle in the uterus contract. These involuntary contractions can be either dull or sharp and intense.
It can take up to 2 years from menarche for a girl's body to develop a regular menstrual cycle. During that time, her body is adjusting to the hormones puberty brings. On average, the monthly cycle for an adult woman is 28 days, but the range is from 23 to 35 days.
Fertilization
If a female and male have sex within several days of the female's ovulation, fertilization can occur. When the male ejaculates (when semen leaves a male's penis), between 0.05 and 0.2 fluid ounces (1.5 to 6.0 milliliters) of semen is deposited into the vagina. Between 75 and 900 million sperm are in this small amount of semen, and they "swim" up from the vagina through the cervix and uterus to meet the egg in the fallopian tube. It takes only one sperm to fertilize the egg.
About a week after the sperm fertilizes the egg, the fertilized egg (zygote) has become a multicelled blastocyst. A blastocyst is about the size of a pinhead, and it's a hollow ball of cells with fluid inside. The blastocyst burrows itself into the lining of the uterus, called the endometrium. The hormone estrogen causes the endometrium to become thick and rich with blood. Progesterone, another hormone released by the ovaries, keeps the endometrium thick with blood so that the blastocyst can attach to the uterus and absorb nutrients from it. This process is called implantation.
As cells from the blastocyst take in nourishment, another stage of development, the embryonic stage, begins. The inner cells form a flattened circular shape called the embryonic disk, which will develop into a baby. The outer cells become thin membranes that form around the baby. The cells multiply thousands of times and move to new positions to eventually become the embryo.
After approximately 8 weeks, the embryo is about the size of an adult's thumb, but almost all of its parts — the brain and nerves, the heart and blood, the stomach and intestines, and the muscles and skin — have formed.
During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus floats in amniotic fluid inside the amniotic sac. The fetus receives oxygen and nourishment from the mother's blood via the placenta, a disk-like structure that sticks to the inner lining of the uterus and connects to the fetus via the umbilical cord. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother's body.
Pregnancy lasts an average of 280 days — about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. The mucus that has formed a plug in the cervix loosens, and with amniotic fluid, comes out through the vagina when the mother's water breaks.
When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin. The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The baby's head usually comes first; the umbilical cord comes out with the baby and is cut after the baby is delivered.
The last stage of the birth process involves the delivery of the placenta, which at that point is called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.
Problems of the Female Reproductive System
Some girls might experience reproductive system problems, such as:
Problems of the Vulva and Vagina
Vulvovaginitis is an inflammation of the vulva and vagina. It may be caused by irritating substances (such as laundry soaps or bubble baths) or poor personal hygiene (such as wiping from back to front after a bowel movement). Symptoms include redness and itching in the vaginal and vulvar areas and sometimes vaginal discharge. Vulvovaginitis also can be caused by an overgrowth of Candida, a fungus normally present in the vagina.
Nonmenstrual vaginal bleeding is most commonly due to the presence of a vaginal foreign body, often wadded-up toilet paper. It may also be due to urethral prolapse, in which the mucous membranes of the urethra protrude into the vagina and form a tiny, doughnut-shaped mass of tissue that bleeds easily. It also can be due to a straddle injury (such as when falling onto a gymnastics beam or bicycle frame) or vaginal trauma from sexual abuse.
Labial adhesions, the sticking together or adherence of the labia in the midline, usually appear in infants and young girls. Although there are usually no symptoms associated with this condition, labial adhesions can lead to an increased risk of urinary tract infection. Sometimes topical estrogen cream is used to help separate the labia.
Problems of the Ovaries and Fallopian Tubes
Ectopic pregnancy occurs when a fertilized egg, or zygote, doesn't travel into the uterus, but instead grows rapidly in the fallopian tube. A woman with this condition can develop severe abdominal pain and should see a doctor because surgery may be necessary.
Endometriosis occurs when tissue normally found only in the uterus starts to grow outside the uterus — in the ovaries, fallopian tubes, or other parts of the pelvic cavity. It can cause abnormal bleeding, painful periods, and general pelvic pain.
Ovarian tumors, although they're rare, can occur. Girls with ovarian tumors may have abdominal pain and masses that can be felt in the abdomen. Surgery may be needed to remove the tumor.
Ovarian cysts are noncancerous sacs filled with fluid or semisolid material. Although they are common and generally harmless, they can become a problem if they grow very large. Large cysts may push on surrounding organs, causing abdominal pain. In most cases, cysts will disappear on their own and treatment is unnecessary. If the cysts are painful, a doctor may prescribe birth control pills to alter their growth or they may be removed by a surgeon.
Polycystic ovary syndrome is a hormone disorder in which too many male hormones (androgens) are produced by the ovaries. This condition causes the ovaries to become enlarged and develop many fluid-filled sacs, or cysts. It often first appears during the teen years. Depending on the type and severity of the condition, it may be treated with drugs to regulate hormone balance and menstruation.
Ovarian torsion, or the twisting of the ovary, can occur when an ovary becomes twisted because of a disease or a developmental abnormality. The torsion blocks blood from flowing through the blood vessels that supply and nourish the ovaries. The most common symptom is lower abdominal pain. Surgery is usually necessary to correct it.
Menstrual Problems
A variety of menstrual problems can affect girls, including:
Dysmenorrhea is when a girl has painful periods.
Menorrhagia is when a girl has a very heavy periods with excess bleeding.
Oligomenorrhea is when a girl misses or has infrequent periods, even though she's been menstruating for a while and isn't pregnant.
Amenorrhea is when a girl has not started her period by the time she is 16 years old or 3 years after starting puberty, has not developed signs of puberty by age 14, or has had normal periods but has stopped menstruating for some reason other than pregnancy.
Infections of the Female Reproductive System
Sexually transmitted infections (STIs). These include infections and diseases such as pelvic inflammatory disease (PID), human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), human papillomavirus (HPV, or genital warts), syphilis, chlamydia, gonorrhea, and genital herpes (HSV). Most are spread from one person to another by sexual contact.
Toxic shock syndrome. This uncommon illness is caused by toxins released into the body during a type of bacterial infection that is more likely to develop if a tampon is left in too long. It can produce high fever, diarrhea, vomiting, and shock.
If you think your daughter may have symptoms of a problem with her reproductive system or if you have questions about her growth and development, talk to your doctor — many problems with the female reproductive system can be treated.
"I pray that this article empowers you to Get A L.I.F.E."
Saturday, May 14, 2011
The Eyes
We depend on sight more than any other of our senses to maneuver through the space around us. In a single glance, lasting a fraction of a second, our eyes work with our brains to tell us the size, shape, color, and texture of an object. They let us know how close it is, whether it's standing still or coming toward us, and how quickly it's moving. Every day, our eyes give us messages that help us understand the world around us.
Although the eyes are small compared with most of the body's other organs, their structure is incredibly complex. The eyes work together to perceive depth, enabling us to judge distance and the size of objects to help us move around them. Not only do the two eyes work together, they also work with the brain, muscles, and nerves to produce complicated visual images and messages. And our eyes constantly adapt to the changing environment — for example, they are able to adjust so that we can easily move around in a nearly dark room or bright sunlight.
To understand more about how the eyes work, it's important to know about the structures that make up the eye and about conditions and diseases that can interfere with vision.
How Eyes Work
Only part of the eye is visible in a person's face. The whole eye — the eyeball — is about the size and shape of a ping-pong ball.
The eye — both the parts that are visible and those that aren't — is extremely delicate. The body has several ways of protecting this vulnerable organ. The eyeball sits in the eye socket (also called the orbit) in a person's skull, where it is surrounded by bone. The visible part of the eye is protected by the eyelids and the eyelashes, which keep dirt, dust, and even harmful bright light out of the eye.
Our eyes are also protected by tears, which moisten the eyes and clean out dirt, dust, and other irritants that get past the defenses of our eyelashes and eyelids. Tears also help protect the eyes against infection.
Every time we blink, our eyelids spread a layer of mucus, oil, and tears over the cornea, which covers the eye. The lacrimal glands in the upper outer corner of each eye socket produce tears.
After they've done their job moistening the eyes, the tears flow into canals in the eyelids, which drain into the lacrimal sac, a pouch in the lower inner corner of each eye socket. Tears then exit through a passage which leads to the nose.
To see, the eye has to move. Six muscles, called extraocular muscles, surround the eyeball in the skull. These muscles act like the strings on a puppet, moving the eye in different directions. The muscles of each eye normally move together at the same time, allowing the two eyes to remain aligned.
The wall of a person's eyeball is made up of three layers, rather like the layers on an onion:
1. The sclera is the outermost protective layer. This tough, fibrous tissue surrounds the eyeball and attaches to the cornea, which is the clear front surface of the eye. What we see as the white of the eye is the sclera. Over the sclera lies the conjunctiva, a clear mucous membrane that protects the eye from becoming dry.
2. The choroid is the middle layer that contains blood vessels that deliver oxygen and nutrients to the retina.
3. The retina, the innermost of the three layers, lines the inside of the eyeball. The retina is a soft, light-sensitive layer of nervous system tissue. The optic nerve carries signals from the retina to the brain, which interprets them as visual images.
The space in the center of the eyeball is filled with a clear jelly-like material called the vitreous humor. This material allows light to pass through to the retina. It also helps the eye keep its round shape.
Vision is the process by which images captured by the eye are interpreted by the brain, and the visible part of the eye is where the process of sight begins. On the front surface of the eye is the see-through, circle-shaped cornea. You can't see a person's cornea the way you can see the colored part of the eye behind it — the cornea is like a clear window that focuses light into the eye. Behind the cornea is a watery fluid called the aqueous humor. The cornea and aqueous humor form an outer lens that refracts (bends) light on its way into the eye. This is where most of the eye's focusing work is done.
The colored circular membrane in the eye just behind the cornea is called the iris. The iris controls the amount of light entering the eye through the pupil, which is the opening in the center of the iris that looks like a tiny black circle. Like a camera, which controls the amount of light coming in to prevent both overexposure and underexposure, the iris becomes wider and narrower, changing the size of the pupil to control the amount of light entering the eye. The pupil gets bigger when more light is needed to see better and smaller when there's plenty of light.
The eye's lens sits just behind the iris. Just like a camera lens, the eye's lens focuses light to form sharp, clear images. Light that has been focused through the cornea and aqueous humor hits the lens, which then focuses it further, sending the light rays through the vitreous humor and onto the retina.
To focus on objects clearly at varying distances, the eye's lens needs to change shape. The ciliary body contains the muscular structure in the eye that changes the shape of the eye's lens. In people who have normal vision, the ciliary body flattens the lens enough to bring objects into focus at a distance of 20 feet or more. To see closer objects, this muscle contracts to thicken the lens. Young children can see objects at very close range; many people over 45 have to hold objects farther and farther away to see them clearly. This is because the lens becomes less elastic as we age.
The retina (the soft, light-sensitive layer of tissue that lines the back of the eyeball wall) is made up of millions of light receptors. These are called rods and cones. Rods are much more sensitive to light than cones. Each eye has about 125 million rods that help us see in dim light and detect shades of gray, but they cannot distinguish colors. In comparison, the 6 million cones in each eye allow us to see in bright light, and they also sense color and detail.
The macula is a small, specialized area on the retina. The macula helps our eyes see fine details when we look directly at an object. It contains mainly cones and few rods.
When focused light is projected onto the retina, it stimulates the rods and cones. The retina then sends nerve signals are sent through the back of the eye to the optic nerve. The optic nerve carries these signals to the brain, which interprets them as visual images. The portion of the brain that processes visual input and interprets the messages that the eye sends is called the visual cortex.
As in a camera, the eye's lens transmits light patterns upside down. The brain learns that the impulses received from the upper part of the retina are really from the lower part of the object we're seeing and vice versa.
Most people use both eyes to see an object. This is called binocular vision. Through binocular vision, images are formed on the retina of each eye. These images are slightly different, because the object is being viewed from slightly different angles. Nerve signals representing each image are sent to the brain, where they are interpreted as two views of the same object. Some of the nerve fibers from each eye cross, so each side of the brain receives messages from both eyes. Through experience, the brain learns to judge the distance of an object by the degree of difference in the images it receives from the two eyes. This ability to sense distance is called depth perception.
Vision is a fine-tuned process. All the parts of the eye — and the brain — need to work together so a person can see correctly. Because the eye's structure is so complex, though, a lot of things can go wrong.
Vision Problems
Some of the most common eye problems are refractive errors. These are the problems that eye doctors check for routinely in a vision test. Refraction means bending of light rays to focus the light coming from an image. Refractive errors are problems with the focusing of the eye, because of the way the eye is shaped, which causes the image you see to be blurred.
Refractive errors include:
Astigmatism. In astigmatism, there's a problem with the curve of the cornea. This causes part of the eye's image to be blurry. Corrective lenses such as contact lenses or glasses can usually correct vision in people with astigmatism.
Nearsightedness. Also called myopia or shortsightedness, nearsightedness occurs when the eye focuses the image of an object in front of the retina instead of directly on it. In most cases, people can't see well far away, but can see objects clearly close up. The condition tends to get somewhat worse through childhood and adolescence, but stabilizes in adulthood. People with this condition may need to wear glasses or contacts to correct their vision. Laser eye surgery is now commonly used in adults to correct nearsightedness permanently by changing the shape of the cornea. Laser surgery is not used in kids and teens because the eye may still be growing and the refractive error changing.
Farsightedness. Also called hyperopia or longsightedness, farsightedness occurs when the incoming image is not focused on the retina, but behind it. This makes it difficult to see close objects clearly, even though far-off objects can be seen clearly. Glasses or contact lenses can correct this problem in kids and teens. Most adults develop a form of farsightedness called presbyopia as they get older.
Some of the other eye problems that can affect children and teens include:
Blindness. This is the loss of useful sight. Blindness can be temporary or permanent and it has many causes. Birth defects or damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. The visual impairment cannot be corrected with surgery or corrective lenses, and the condition can make it difficult to perform everyday activities. Diabetes, problems with the macula, and eye changes because of aging account for most blindness in the United States.
Cataracts. Some children are born with cataracts, a cloudiness of the eye's lenses that prevent images from being seen clearly or at all. But cataracts are much more prevalent in the elderly among whom surgery to remove cataracts and correct vision is common. In infants and young children, cataracts must be treated to prevent permanent problems with development of vision.
Color blindness. Color blindness is caused by problems in the pigments of the cones in the retina. Most people who are color-blind can see some colors. In most cases, someone who is color-blind confuses some colors with others, usually red and green. People can be born color-blind or they may develop the condition over time. The most common form of color blindness is an inherited condition that affects boys much more often than girls. Color blindness cannot be corrected.
Conjunctivitis. Conjunctivitis refers to inflammation (redness, pain, and swelling) of the conjunctiva. One type of conjunctivitis is called pinkeye, a common contagious infection in which the eyes become pinkish red and watery, and pus may form. Pinkeye is usually treated with eyedrops. Conjunctivitis may also occur due to allergies or from a scratch on the surface of the eye.
Dacryostenosis. Dacryostenosis is a blockage of the tear drainage system of the eye occurring in the lower eyelid. This is a fairly common problem in infants, but often improves with time.
Eye injuries. Injuries to the eye are one of the most common preventable causes of blindness. Eye injuries may be caused by irritants such as sand, dirt, or other foreign bodies on the eye's surface. Chemicals or foreign bodies that become embedded in the eye can also cause pain and loss of vision. Forceful blows to the eye can cause bleeding inside the eye and damage to the cornea, retina, and other important eye structures.
Glaucoma. One of the leading causes of blindness in the United States, glaucoma is a disorder that causes fluid pressure to build up inside the eye, potentially causing damage to the optic nerve. Although it can occur in infants and children, it is much more common among older adults. Unless detected early by routine screening tests, it usually goes undiagnosed until some vision is lost.
Macular degeneration is an eye disease that mainly affects older people. But sometimes infants and children can develop it, too. When someone has macular degeneration, the middle area of the retina becomes scarred. This causes eyesight to deteriorate over many years. The cause of macular degeneration is unknown in most cases, but it tends to run in families, which indicates that genes and heredity are involved.
Retinoblastoma. This is a cancerous tumor in the eye that usually appears in the first 5 years of life. There may be permanent vision loss, and the affected eye(s) may have to be removed.
Retinopathy of prematurity. Premature babies sometimes have damage to the blood vessels in the eye's retina, a condition known as retinopathy of prematurity, which can lead to severe vision loss in some cases.
Strabismus. A condition in which the eyes appear crossed, strabismus is usually caused by a defect in the balance of the pull exerted by the muscles that help the eyes stay straight and move together properly. Surgery on the eye muscles can help realign the eyes. Permanent vision loss in the less-used eye (amblyopia) can occur if the condition is not treated in early childhood.
Sty. A sty is an infection of one of the follicles from which the eyelashes grow. Sties are treated by applying warm compresses and using antibiotics.
Proper care of your child's eyes includes having periodic eye exams at routine office checkups and by an eye specialist according to the schedule recommended by your doctor. Signs that a very young child may be having vision trouble include constant eye rubbing, tearing or redness, and trouble following an object. Older kids may squint or sit too close to the TV. Kids who are having trouble seeing might also complain of headaches at the end of the day.
"I pray that this article empowers you to Get A L.I.F.E."
Although the eyes are small compared with most of the body's other organs, their structure is incredibly complex. The eyes work together to perceive depth, enabling us to judge distance and the size of objects to help us move around them. Not only do the two eyes work together, they also work with the brain, muscles, and nerves to produce complicated visual images and messages. And our eyes constantly adapt to the changing environment — for example, they are able to adjust so that we can easily move around in a nearly dark room or bright sunlight.
To understand more about how the eyes work, it's important to know about the structures that make up the eye and about conditions and diseases that can interfere with vision.
How Eyes Work
Only part of the eye is visible in a person's face. The whole eye — the eyeball — is about the size and shape of a ping-pong ball.
The eye — both the parts that are visible and those that aren't — is extremely delicate. The body has several ways of protecting this vulnerable organ. The eyeball sits in the eye socket (also called the orbit) in a person's skull, where it is surrounded by bone. The visible part of the eye is protected by the eyelids and the eyelashes, which keep dirt, dust, and even harmful bright light out of the eye.
Our eyes are also protected by tears, which moisten the eyes and clean out dirt, dust, and other irritants that get past the defenses of our eyelashes and eyelids. Tears also help protect the eyes against infection.
Every time we blink, our eyelids spread a layer of mucus, oil, and tears over the cornea, which covers the eye. The lacrimal glands in the upper outer corner of each eye socket produce tears.
After they've done their job moistening the eyes, the tears flow into canals in the eyelids, which drain into the lacrimal sac, a pouch in the lower inner corner of each eye socket. Tears then exit through a passage which leads to the nose.
To see, the eye has to move. Six muscles, called extraocular muscles, surround the eyeball in the skull. These muscles act like the strings on a puppet, moving the eye in different directions. The muscles of each eye normally move together at the same time, allowing the two eyes to remain aligned.
The wall of a person's eyeball is made up of three layers, rather like the layers on an onion:
1. The sclera is the outermost protective layer. This tough, fibrous tissue surrounds the eyeball and attaches to the cornea, which is the clear front surface of the eye. What we see as the white of the eye is the sclera. Over the sclera lies the conjunctiva, a clear mucous membrane that protects the eye from becoming dry.
2. The choroid is the middle layer that contains blood vessels that deliver oxygen and nutrients to the retina.
3. The retina, the innermost of the three layers, lines the inside of the eyeball. The retina is a soft, light-sensitive layer of nervous system tissue. The optic nerve carries signals from the retina to the brain, which interprets them as visual images.
The space in the center of the eyeball is filled with a clear jelly-like material called the vitreous humor. This material allows light to pass through to the retina. It also helps the eye keep its round shape.
Vision is the process by which images captured by the eye are interpreted by the brain, and the visible part of the eye is where the process of sight begins. On the front surface of the eye is the see-through, circle-shaped cornea. You can't see a person's cornea the way you can see the colored part of the eye behind it — the cornea is like a clear window that focuses light into the eye. Behind the cornea is a watery fluid called the aqueous humor. The cornea and aqueous humor form an outer lens that refracts (bends) light on its way into the eye. This is where most of the eye's focusing work is done.
The colored circular membrane in the eye just behind the cornea is called the iris. The iris controls the amount of light entering the eye through the pupil, which is the opening in the center of the iris that looks like a tiny black circle. Like a camera, which controls the amount of light coming in to prevent both overexposure and underexposure, the iris becomes wider and narrower, changing the size of the pupil to control the amount of light entering the eye. The pupil gets bigger when more light is needed to see better and smaller when there's plenty of light.
The eye's lens sits just behind the iris. Just like a camera lens, the eye's lens focuses light to form sharp, clear images. Light that has been focused through the cornea and aqueous humor hits the lens, which then focuses it further, sending the light rays through the vitreous humor and onto the retina.
To focus on objects clearly at varying distances, the eye's lens needs to change shape. The ciliary body contains the muscular structure in the eye that changes the shape of the eye's lens. In people who have normal vision, the ciliary body flattens the lens enough to bring objects into focus at a distance of 20 feet or more. To see closer objects, this muscle contracts to thicken the lens. Young children can see objects at very close range; many people over 45 have to hold objects farther and farther away to see them clearly. This is because the lens becomes less elastic as we age.
The retina (the soft, light-sensitive layer of tissue that lines the back of the eyeball wall) is made up of millions of light receptors. These are called rods and cones. Rods are much more sensitive to light than cones. Each eye has about 125 million rods that help us see in dim light and detect shades of gray, but they cannot distinguish colors. In comparison, the 6 million cones in each eye allow us to see in bright light, and they also sense color and detail.
The macula is a small, specialized area on the retina. The macula helps our eyes see fine details when we look directly at an object. It contains mainly cones and few rods.
When focused light is projected onto the retina, it stimulates the rods and cones. The retina then sends nerve signals are sent through the back of the eye to the optic nerve. The optic nerve carries these signals to the brain, which interprets them as visual images. The portion of the brain that processes visual input and interprets the messages that the eye sends is called the visual cortex.
As in a camera, the eye's lens transmits light patterns upside down. The brain learns that the impulses received from the upper part of the retina are really from the lower part of the object we're seeing and vice versa.
Most people use both eyes to see an object. This is called binocular vision. Through binocular vision, images are formed on the retina of each eye. These images are slightly different, because the object is being viewed from slightly different angles. Nerve signals representing each image are sent to the brain, where they are interpreted as two views of the same object. Some of the nerve fibers from each eye cross, so each side of the brain receives messages from both eyes. Through experience, the brain learns to judge the distance of an object by the degree of difference in the images it receives from the two eyes. This ability to sense distance is called depth perception.
Vision is a fine-tuned process. All the parts of the eye — and the brain — need to work together so a person can see correctly. Because the eye's structure is so complex, though, a lot of things can go wrong.
Vision Problems
Some of the most common eye problems are refractive errors. These are the problems that eye doctors check for routinely in a vision test. Refraction means bending of light rays to focus the light coming from an image. Refractive errors are problems with the focusing of the eye, because of the way the eye is shaped, which causes the image you see to be blurred.
Refractive errors include:
Astigmatism. In astigmatism, there's a problem with the curve of the cornea. This causes part of the eye's image to be blurry. Corrective lenses such as contact lenses or glasses can usually correct vision in people with astigmatism.
Nearsightedness. Also called myopia or shortsightedness, nearsightedness occurs when the eye focuses the image of an object in front of the retina instead of directly on it. In most cases, people can't see well far away, but can see objects clearly close up. The condition tends to get somewhat worse through childhood and adolescence, but stabilizes in adulthood. People with this condition may need to wear glasses or contacts to correct their vision. Laser eye surgery is now commonly used in adults to correct nearsightedness permanently by changing the shape of the cornea. Laser surgery is not used in kids and teens because the eye may still be growing and the refractive error changing.
Farsightedness. Also called hyperopia or longsightedness, farsightedness occurs when the incoming image is not focused on the retina, but behind it. This makes it difficult to see close objects clearly, even though far-off objects can be seen clearly. Glasses or contact lenses can correct this problem in kids and teens. Most adults develop a form of farsightedness called presbyopia as they get older.
Some of the other eye problems that can affect children and teens include:
Blindness. This is the loss of useful sight. Blindness can be temporary or permanent and it has many causes. Birth defects or damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. The visual impairment cannot be corrected with surgery or corrective lenses, and the condition can make it difficult to perform everyday activities. Diabetes, problems with the macula, and eye changes because of aging account for most blindness in the United States.
Cataracts. Some children are born with cataracts, a cloudiness of the eye's lenses that prevent images from being seen clearly or at all. But cataracts are much more prevalent in the elderly among whom surgery to remove cataracts and correct vision is common. In infants and young children, cataracts must be treated to prevent permanent problems with development of vision.
Color blindness. Color blindness is caused by problems in the pigments of the cones in the retina. Most people who are color-blind can see some colors. In most cases, someone who is color-blind confuses some colors with others, usually red and green. People can be born color-blind or they may develop the condition over time. The most common form of color blindness is an inherited condition that affects boys much more often than girls. Color blindness cannot be corrected.
Conjunctivitis. Conjunctivitis refers to inflammation (redness, pain, and swelling) of the conjunctiva. One type of conjunctivitis is called pinkeye, a common contagious infection in which the eyes become pinkish red and watery, and pus may form. Pinkeye is usually treated with eyedrops. Conjunctivitis may also occur due to allergies or from a scratch on the surface of the eye.
Dacryostenosis. Dacryostenosis is a blockage of the tear drainage system of the eye occurring in the lower eyelid. This is a fairly common problem in infants, but often improves with time.
Eye injuries. Injuries to the eye are one of the most common preventable causes of blindness. Eye injuries may be caused by irritants such as sand, dirt, or other foreign bodies on the eye's surface. Chemicals or foreign bodies that become embedded in the eye can also cause pain and loss of vision. Forceful blows to the eye can cause bleeding inside the eye and damage to the cornea, retina, and other important eye structures.
Glaucoma. One of the leading causes of blindness in the United States, glaucoma is a disorder that causes fluid pressure to build up inside the eye, potentially causing damage to the optic nerve. Although it can occur in infants and children, it is much more common among older adults. Unless detected early by routine screening tests, it usually goes undiagnosed until some vision is lost.
Macular degeneration is an eye disease that mainly affects older people. But sometimes infants and children can develop it, too. When someone has macular degeneration, the middle area of the retina becomes scarred. This causes eyesight to deteriorate over many years. The cause of macular degeneration is unknown in most cases, but it tends to run in families, which indicates that genes and heredity are involved.
Retinoblastoma. This is a cancerous tumor in the eye that usually appears in the first 5 years of life. There may be permanent vision loss, and the affected eye(s) may have to be removed.
Retinopathy of prematurity. Premature babies sometimes have damage to the blood vessels in the eye's retina, a condition known as retinopathy of prematurity, which can lead to severe vision loss in some cases.
Strabismus. A condition in which the eyes appear crossed, strabismus is usually caused by a defect in the balance of the pull exerted by the muscles that help the eyes stay straight and move together properly. Surgery on the eye muscles can help realign the eyes. Permanent vision loss in the less-used eye (amblyopia) can occur if the condition is not treated in early childhood.
Sty. A sty is an infection of one of the follicles from which the eyelashes grow. Sties are treated by applying warm compresses and using antibiotics.
Proper care of your child's eyes includes having periodic eye exams at routine office checkups and by an eye specialist according to the schedule recommended by your doctor. Signs that a very young child may be having vision trouble include constant eye rubbing, tearing or redness, and trouble following an object. Older kids may squint or sit too close to the TV. Kids who are having trouble seeing might also complain of headaches at the end of the day.
"I pray that this article empowers you to Get A L.I.F.E."
Saturday, March 12, 2011
The Endocrine System
Endocrine System
Although we rarely think about them, the glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.
In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.
About the Endocrine System
The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Although many different hormones circulate throughout the bloodstream, each one affects only the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood.
A gland is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere in the body. Some types of glands release their secretions in specific areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretions in the skin or inside of the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.
Parts of the Endocrine System
The major glands that make up the human endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes. The pancreas is also part of this hormone-secreting system, even though it is also associated with the digestive system because it also produces and secretes digestive enzymes.
Although the endocrine glands are the body's main hormone producers, some non-endocrine organs — such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta — also produce and release hormones.
The Hypothalamus
The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.
Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands. The production and secretion of pituitary hormones can be influenced by factors such as emotions and seasonal changes. To accomplish this, the hypothalamus relays information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary.
The Pituitary Gland
The tiny pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. Among the hormones it produces are:
growth hormone, which stimulates the growth of bone and other body
tissues and plays a role in the body's handling of nutrients and
minerals
prolactin, which activates milk production in women who are
breastfeeding
thyrotropin, which stimulates the thyroid gland to produce thyroid
hormones
corticotropin, which stimulates the adrenal gland to produce certain
hormones
The pituitary also secretes endorphins, chemicals that act on the nervous system to reduce sensitivity to pain. In addition, the pituitary secretes hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women.
The posterior lobe of the pituitary releases antidiuretic hormone, which helps control body water balance through its effect on the kidneys and urine output; and oxytocin, which triggers the contractions of the uterus that occur during labor.
The Thyroid and Parathyroids
The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine and triiodothyronine. These hormones control the rate at which cells burn fuels from food to produce energy. As the level of thyroid hormones increases in the bloodstream, so does the speed at which chemical reactions occur in the body.
Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. The production and release of thyroid hormones is controlled by thyrotropin, which is secreted by the pituitary gland.
Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin, which is produced in the thyroid.
The Adrenal Glands
The body has two triangular adrenal glands, one on top of each kidney. The adrenal glands have two parts, each of which produces a set of hormones and has a different function. The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.
The inner part, the adrenal medulla, produces catecholamines, such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress. (Epinephrine injections are often used to counteract a severe allergic reaction.)
The Pineal Gland and Gonads
The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle.
The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonads, or testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development, including enlargement of the penis, the growth spurt that occurs during puberty, and the appearance of other male secondary sex characteristics such as deepening of the voice, growth of facial and pubic hair, and the increase in muscle growth and strength. Working with hormones from the pituitary gland, testosterone also supports the production of sperm by the testes.
The female gonads, the ovaries, are located in the pelvis. They produce eggs and secrete the female hormones estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in pregnancy and the regulation of the menstrual cycle.
The pancreas produces (in addition to others) two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.
What the Endocrine System Does
Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to target cells designed to receive its message. Along the way to the target cells, special proteins bind to some of the hormones. The special proteins act as carriers that control the amount of hormone that is available to interact with and affect the target cells.
Also, the target cells have receptors that latch onto only specific hormones, and each hormone has its own receptor, so that each hormone will communicate only with specific target cells that possess receptors for that hormone. When the hormone reaches its target cell, it locks onto the cell's specific receptors and these hormone-receptor combinations transmit chemical instructions to the inner workings of the cell.
When hormone levels reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms to maintain that level of hormone in the blood. This regulation of hormone secretion may involve the hormone itself or another substance in the blood related to the hormone.
For example, if the thyroid gland has secreted adequate amounts of thyroid hormones into the blood, the pituitary gland senses the normal levels of thyroid hormone in the bloodstream and adjusts its release of thyrotropin, the pituitary hormone that stimulates the thyroid gland to produce thyroid hormones.
Another example is parathyroid hormone, which increases the level of calcium in the blood. When the blood calcium level rises, the parathyroid glands sense the change and decrease their secretion of parathyroid hormone. This turnoff process is called a negative feedback system.
Problems With the Endocrine System
Too much or too little of any hormone can be harmful to the body. For example, if the pituitary gland produces too much growth hormone, a child may grow excessively tall. If it produces too little, a child may be abnormally short.
Controlling the production of or replacing specific hormones can treat many endocrine disorders in children and adolescents, some of which include:
Adrenal insufficiency. This condition is characterized by decreased function of the adrenal cortex and the consequent underproduction of adrenal corticosteroid hormones. The symptoms of adrenal insufficiency may include weakness, fatigue, abdominal pain, nausea, dehydration, and skin changes. Doctors treat adrenal insufficiency by giving replacement corticosteroid hormones.
Cushing syndrome. Excessive amounts of glucocorticoid hormones in the body can lead to Cushing syndrome. In children, it most often results when a child takes large doses of synthetic corticosteroid drugs (such as prednisone) to treat autoimmune diseases such as lupus. If the condition is due to a tumor in the pituitary gland that produces excessive amounts of corticotropin and stimulates the adrenals to overproduce corticosteroids, it's known as Cushing disease. Symptoms may take years to develop and include obesity, growth failure, muscle weakness, easy bruising of the skin, acne, high blood pressure, and psychological changes. Depending on the specific cause, doctors may treat this condition with surgery, radiation therapy, chemotherapy, or drugs that block the production of hormones.
Type 1 diabetes. When the pancreas fails to produce enough insulin, type 1 diabetes (previously known as juvenile diabetes) occurs. Symptoms include excessive thirst, hunger, urination, and weight loss. In children and teens, the condition is usually an autoimmune disorder in which specific immune system cells and antibodies produced by the immune system attack and destroy the cells of the pancreas that produce insulin. The disease can cause long-term complications including kidney problems, nerve damage, blindness, and early coronary heart disease and stroke. To control their blood sugar levels and reduce the risk of developing diabetes complications, kids with this condition need regular injections of insulin.
Type 2 diabetes. Unlike type 1 diabetes, in which the body can't produce normal amounts of insulin, in type 2 diabetes the body is unable to respond to insulin normally. Children and teens with the condition tend to be overweight, and it is believed that excess body fat plays a role in the insulin resistance that characterizes the disease. In fact, the rising prevalence of this type of diabetes in kids has paralleled the dramatically increasing rates of obesity among kids in recent years. The symptoms and possible complications of type 2 diabetes are basically the same as those of type 1. Some kids and teens can control their blood sugar level with dietary changes, exercise, and oral medications, but many will need to take insulin injections like patients with type 1 diabetes.
Growth hormone problems. Too much growth hormone in children who are still growing will make their bones and other body parts grow excessively, resulting in gigantism. This rare condition is usually caused by a pituitary tumor and can be treated by removing the tumor. In contrast, when the pituitary gland fails to produce adequate amounts of growth hormone, a child's growth in height is impaired. Hypoglycemia (low blood sugar) may also occur in kids with growth hormone deficiency, particularly in infants and young children with the condition.
Hyperthyroidism. Hyperthyroidism is a condition in which the levels of thyroid hormones in the blood are excessively high. Symptoms may include weight loss, nervousness, tremors, excessive sweating, increased heart rate and blood pressure, protruding eyes, and a swelling in the neck from an enlarged thyroid gland (goiter). In kids the condition is usually caused by Graves' disease, an autoimmune disorder in which specific antibodies produced by the immune system stimulate the thyroid gland to become overactive. The disease may be controlled with medications or by removal or destruction of the thyroid gland through surgery or radiation treatments.
Hypothyroidism. Hypothyroidism is a condition in which the levels of thyroid hormones in the blood are abnormally low. Thyroid hormone deficiency slows body processes and may lead to fatigue, a slow heart rate, dry skin, weight gain, constipation, and, in kids, slowing of growth and delayed puberty. Hashimoto's thyroiditis, which results from an autoimmune process that damages the thyroid and blocks thyroid hormone production, is the most common cause of hypothyroidism in kids. Infants can also be born with an absent or underdeveloped thyroid gland, resulting in hypothyroidism. It can be treated with oral thyroid hormone replacement.
Precocious puberty. Body changes associated with puberty may occur at an abnormally young age in some kids if the pituitary hormones that stimulate the gonads to produce sex hormones rise prematurely. An injectable medication is available that can suppress the secretion of these pituitary hormones (known as gonadotropins) and arrest the progression of sexual development in most of these children.
"I pray that this article empowers you to Get A L.I.F.E."
Although we rarely think about them, the glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.
In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.
About the Endocrine System
The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Although many different hormones circulate throughout the bloodstream, each one affects only the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood.
A gland is a group of cells that produces and secretes, or gives off, chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere in the body. Some types of glands release their secretions in specific areas. For instance, exocrine glands, such as the sweat and salivary glands, release secretions in the skin or inside of the mouth. Endocrine glands, on the other hand, release more than 20 major hormones directly into the bloodstream where they can be transported to cells in other parts of the body.
Parts of the Endocrine System
The major glands that make up the human endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes. The pancreas is also part of this hormone-secreting system, even though it is also associated with the digestive system because it also produces and secretes digestive enzymes.
Although the endocrine glands are the body's main hormone producers, some non-endocrine organs — such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta — also produce and release hormones.
The Hypothalamus
The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary.
Although it is no bigger than a pea, the pituitary gland, located at the base of the brain just beneath the hypothalamus, is considered the most important part of the endocrine system. It's often called the "master gland" because it makes hormones that control several other endocrine glands. The production and secretion of pituitary hormones can be influenced by factors such as emotions and seasonal changes. To accomplish this, the hypothalamus relays information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary.
The Pituitary Gland
The tiny pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. Among the hormones it produces are:
growth hormone, which stimulates the growth of bone and other body
tissues and plays a role in the body's handling of nutrients and
minerals
prolactin, which activates milk production in women who are
breastfeeding
thyrotropin, which stimulates the thyroid gland to produce thyroid
hormones
corticotropin, which stimulates the adrenal gland to produce certain
hormones
The pituitary also secretes endorphins, chemicals that act on the nervous system to reduce sensitivity to pain. In addition, the pituitary secretes hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women.
The posterior lobe of the pituitary releases antidiuretic hormone, which helps control body water balance through its effect on the kidneys and urine output; and oxytocin, which triggers the contractions of the uterus that occur during labor.
The Thyroid and Parathyroids
The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxine and triiodothyronine. These hormones control the rate at which cells burn fuels from food to produce energy. As the level of thyroid hormones increases in the bloodstream, so does the speed at which chemical reactions occur in the body.
Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. The production and release of thyroid hormones is controlled by thyrotropin, which is secreted by the pituitary gland.
Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin, which is produced in the thyroid.
The Adrenal Glands
The body has two triangular adrenal glands, one on top of each kidney. The adrenal glands have two parts, each of which produces a set of hormones and has a different function. The outer part, the adrenal cortex, produces hormones called corticosteroids that influence or regulate salt and water balance in the body, the body's response to stress, metabolism, the immune system, and sexual development and function.
The inner part, the adrenal medulla, produces catecholamines, such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body experiences stress. (Epinephrine injections are often used to counteract a severe allergic reaction.)
The Pineal Gland and Gonads
The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle.
The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonads, or testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development, including enlargement of the penis, the growth spurt that occurs during puberty, and the appearance of other male secondary sex characteristics such as deepening of the voice, growth of facial and pubic hair, and the increase in muscle growth and strength. Working with hormones from the pituitary gland, testosterone also supports the production of sperm by the testes.
The female gonads, the ovaries, are located in the pelvis. They produce eggs and secrete the female hormones estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in pregnancy and the regulation of the menstrual cycle.
The pancreas produces (in addition to others) two important hormones, insulin and glucagon. They work together to maintain a steady level of glucose, or sugar, in the blood and to keep the body supplied with fuel to produce and maintain stores of energy.
What the Endocrine System Does
Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to target cells designed to receive its message. Along the way to the target cells, special proteins bind to some of the hormones. The special proteins act as carriers that control the amount of hormone that is available to interact with and affect the target cells.
Also, the target cells have receptors that latch onto only specific hormones, and each hormone has its own receptor, so that each hormone will communicate only with specific target cells that possess receptors for that hormone. When the hormone reaches its target cell, it locks onto the cell's specific receptors and these hormone-receptor combinations transmit chemical instructions to the inner workings of the cell.
When hormone levels reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms to maintain that level of hormone in the blood. This regulation of hormone secretion may involve the hormone itself or another substance in the blood related to the hormone.
For example, if the thyroid gland has secreted adequate amounts of thyroid hormones into the blood, the pituitary gland senses the normal levels of thyroid hormone in the bloodstream and adjusts its release of thyrotropin, the pituitary hormone that stimulates the thyroid gland to produce thyroid hormones.
Another example is parathyroid hormone, which increases the level of calcium in the blood. When the blood calcium level rises, the parathyroid glands sense the change and decrease their secretion of parathyroid hormone. This turnoff process is called a negative feedback system.
Problems With the Endocrine System
Too much or too little of any hormone can be harmful to the body. For example, if the pituitary gland produces too much growth hormone, a child may grow excessively tall. If it produces too little, a child may be abnormally short.
Controlling the production of or replacing specific hormones can treat many endocrine disorders in children and adolescents, some of which include:
Adrenal insufficiency. This condition is characterized by decreased function of the adrenal cortex and the consequent underproduction of adrenal corticosteroid hormones. The symptoms of adrenal insufficiency may include weakness, fatigue, abdominal pain, nausea, dehydration, and skin changes. Doctors treat adrenal insufficiency by giving replacement corticosteroid hormones.
Cushing syndrome. Excessive amounts of glucocorticoid hormones in the body can lead to Cushing syndrome. In children, it most often results when a child takes large doses of synthetic corticosteroid drugs (such as prednisone) to treat autoimmune diseases such as lupus. If the condition is due to a tumor in the pituitary gland that produces excessive amounts of corticotropin and stimulates the adrenals to overproduce corticosteroids, it's known as Cushing disease. Symptoms may take years to develop and include obesity, growth failure, muscle weakness, easy bruising of the skin, acne, high blood pressure, and psychological changes. Depending on the specific cause, doctors may treat this condition with surgery, radiation therapy, chemotherapy, or drugs that block the production of hormones.
Type 1 diabetes. When the pancreas fails to produce enough insulin, type 1 diabetes (previously known as juvenile diabetes) occurs. Symptoms include excessive thirst, hunger, urination, and weight loss. In children and teens, the condition is usually an autoimmune disorder in which specific immune system cells and antibodies produced by the immune system attack and destroy the cells of the pancreas that produce insulin. The disease can cause long-term complications including kidney problems, nerve damage, blindness, and early coronary heart disease and stroke. To control their blood sugar levels and reduce the risk of developing diabetes complications, kids with this condition need regular injections of insulin.
Type 2 diabetes. Unlike type 1 diabetes, in which the body can't produce normal amounts of insulin, in type 2 diabetes the body is unable to respond to insulin normally. Children and teens with the condition tend to be overweight, and it is believed that excess body fat plays a role in the insulin resistance that characterizes the disease. In fact, the rising prevalence of this type of diabetes in kids has paralleled the dramatically increasing rates of obesity among kids in recent years. The symptoms and possible complications of type 2 diabetes are basically the same as those of type 1. Some kids and teens can control their blood sugar level with dietary changes, exercise, and oral medications, but many will need to take insulin injections like patients with type 1 diabetes.
Growth hormone problems. Too much growth hormone in children who are still growing will make their bones and other body parts grow excessively, resulting in gigantism. This rare condition is usually caused by a pituitary tumor and can be treated by removing the tumor. In contrast, when the pituitary gland fails to produce adequate amounts of growth hormone, a child's growth in height is impaired. Hypoglycemia (low blood sugar) may also occur in kids with growth hormone deficiency, particularly in infants and young children with the condition.
Hyperthyroidism. Hyperthyroidism is a condition in which the levels of thyroid hormones in the blood are excessively high. Symptoms may include weight loss, nervousness, tremors, excessive sweating, increased heart rate and blood pressure, protruding eyes, and a swelling in the neck from an enlarged thyroid gland (goiter). In kids the condition is usually caused by Graves' disease, an autoimmune disorder in which specific antibodies produced by the immune system stimulate the thyroid gland to become overactive. The disease may be controlled with medications or by removal or destruction of the thyroid gland through surgery or radiation treatments.
Hypothyroidism. Hypothyroidism is a condition in which the levels of thyroid hormones in the blood are abnormally low. Thyroid hormone deficiency slows body processes and may lead to fatigue, a slow heart rate, dry skin, weight gain, constipation, and, in kids, slowing of growth and delayed puberty. Hashimoto's thyroiditis, which results from an autoimmune process that damages the thyroid and blocks thyroid hormone production, is the most common cause of hypothyroidism in kids. Infants can also be born with an absent or underdeveloped thyroid gland, resulting in hypothyroidism. It can be treated with oral thyroid hormone replacement.
Precocious puberty. Body changes associated with puberty may occur at an abnormally young age in some kids if the pituitary hormones that stimulate the gonads to produce sex hormones rise prematurely. An injectable medication is available that can suppress the secretion of these pituitary hormones (known as gonadotropins) and arrest the progression of sexual development in most of these children.
"I pray that this article empowers you to Get A L.I.F.E."
Saturday, February 26, 2011
Physical Appearance Matters
How successful you become is mostly up to you. Success also depends on how you're perceived by others. Numerous studies have shown looks can impact career advancement.
Some say physical appearance matters even more to employers than a cover letter.
Researchers have found that facial structure, hair color, and weight all can affect our paychecks. We can't help our genes, but some of them may be helping us more than others.
Here are a a list of physical attributes that boost careers:
If you're a 6-foot tall male
Men who are at least 6' tall make an average salary of $5,525 more than their shorter, 5'5 counterparts, says Harvard University. Another study polled half of all the Fortune 500 companies about the height of their CEOs. On average, male CEOs were three inches taller than the average man at just under 6'.
If you're a skinny woman
New York University sociologist Dalton Conley conducted a study and discovered that a woman's weight negatively impacts her household income and "job prestige." In fact, a 1% increase in body mass results in a 0.6 percentage point decrease in family income.
Another study by Jay Zagorsky titled "Health and Wealth" found that Caucasian women get the most financial slack for higher weight, seeing their wealth drop 12%. In comparison, African-American women who are overweight only see a 7% drop. Men weren't affected.
If you're a woman who's three inches taller than her colleagues
For every three inches taller than average they are, women earn 5 to 8 percent more money than women of average height.
If you're symmetrical
Have one eye that's smaller than the other? It could be costing you some of your paycheck. Symmetry is perhaps the greatest sign of perceived beauty, and people who are attractive make a considerable amount more than everyone else.
If you smile a lot
Rick Wilson of Rice University studied "Fiscal Attraction." He found a correlation between good looks and success. In particular, the better a person looks, the more other people trust them, and trust is a quality most leaders possess. One of his findings also showed that subjects ranked people who were smiling as more trustworthy than people with straight faces.
If you're attractive
Yale's Daniel Hamermesh conducted a study, “Beauty in the Labor Market.” He found that people with above average looks typically received premiums in pay of 5% or more, and that less attractive people "suffered a salary penalty of up to 9%." Hamermesh also writes that attractive men earn 9% more than unattractive men, and attractive women earn 4% more than unattractive women.
But not if you're too attractive
Normally, being pretty is a good thing. It's been proven time and time again that attractive people make more money. Cute babies are held and played with more than others, teachers have higher expectations in the classroom for good-looking children, and hiring decisions are made largely (but often subconsciously) on looks.
One study, Physical Attractiveness Bias in Hiring, shows that beauty can be beastly. When women apply for jobs typically handled by men, they are discriminated against. One of the researchers says, ""In these professions [such as manager of research and development, director of finance, mechanical engineer and construction supervisor], being attractive was highly detrimental to women," said Johnson. This was only the case for women. Extraordinarily attractive men weren't found to be discriminated against.
If you have hair on your head but not on your face
According to The Times, "facial hair has long been considered a potential blight on career advancement." They report the results of a survey: "60% of businessmen without beards or moustaches feel that these features are a bad sign. Some feel that the person can’t be bothered to shave and others that they are hiding something."
63% of men also report that hair loss or balding has negatively affected their careers. US News and World Report discusses how plastic surgery can boost careers, in particular hair implants. "In the corporate world, there's a lot of emphasis on image, and image goes with self-confidence," says Antonio Armani, a Beverly Hills, Calif., cosmetic surgeon who specializes in hair transplants. "I think a lot of people do invest money in improving their looks because they feel this is one way they can go up the corporate ladder."
The American Academy of Facial Plastic and Reconstructive Surgery also reported that two thirds of its members, both men and women, wanted cosmetic surgery because they wanted to "remain competitive in the workplace."
If you're a woman who wears makeup
According to TheGlassHammer, a website designed for women executives, "there is strong statistical evidence to show that women who wear make-up in business get better jobs and are promoted more quickly." And a survey reported in The Times shows that "64 per cent of directors said that women who wore make-up look more professional and 18 per cent of directors said that women who do not wear make-up “look like they can’t be bothered to make an effort”.
If you dress conservatively
Harvard Business Review writes about how dressing professionally and conservatively can advance careers: "Women, in particular, believed that dressing the part was a vital factor in attaining success: 53% of them felt aspiring female execs needed to toe a very conservative line, avoiding flashy make-up, plunging necklines, too-short or too-tight skirts, and long fingernails — exactly the sort of sartorial no-nos UBS spelled out. "Indeed, half the women surveyed and 37% of the men considered appearance and EP to be intrinsically linked; they understood that if you don't look the part of a leader, you're not likely to be given the role.
Far from imagining that appearance is a personal matter, they perceived that looking well-turned-out engenders self confidence, a trait they considered the bedrock of authentic leaders."
If you have great posture
According to Harvard Business School's study, "Power Posing: Brief Nonverbal Displays Affect Neuroendocrine Levels and Risk Tolerance," sitting in a position that oozes confidence (i.e. legs up on your desk, chest puffed out, or leaning forward) will make people deem you powerful.
Why?
It raises testosterone levels by roughly 20% and lowers the stress hormone cortisol by the same. The reverse is also true. If you slouch, cross your legs, or look weak, it works against you. Sitting powerfully for just two minutes can make a psychological difference.
According to the study, "High-power posers were more likely than low-power posers to focus on rewards— 86.36% took an offered gambling risk (only 13.63% were risk averse). In contrast, only 60% of the low-power posers took the risk (and 40% were risk averse).
Finally, high-power posers reported feeling significantly more “powerful” and “in charge.”
"I pray that this article empowers you to Get A L.I.F.E."
Some say physical appearance matters even more to employers than a cover letter.
Researchers have found that facial structure, hair color, and weight all can affect our paychecks. We can't help our genes, but some of them may be helping us more than others.
Here are a a list of physical attributes that boost careers:
If you're a 6-foot tall male
Men who are at least 6' tall make an average salary of $5,525 more than their shorter, 5'5 counterparts, says Harvard University. Another study polled half of all the Fortune 500 companies about the height of their CEOs. On average, male CEOs were three inches taller than the average man at just under 6'.
If you're a skinny woman
New York University sociologist Dalton Conley conducted a study and discovered that a woman's weight negatively impacts her household income and "job prestige." In fact, a 1% increase in body mass results in a 0.6 percentage point decrease in family income.
Another study by Jay Zagorsky titled "Health and Wealth" found that Caucasian women get the most financial slack for higher weight, seeing their wealth drop 12%. In comparison, African-American women who are overweight only see a 7% drop. Men weren't affected.
If you're a woman who's three inches taller than her colleagues
For every three inches taller than average they are, women earn 5 to 8 percent more money than women of average height.
If you're symmetrical
Have one eye that's smaller than the other? It could be costing you some of your paycheck. Symmetry is perhaps the greatest sign of perceived beauty, and people who are attractive make a considerable amount more than everyone else.
If you smile a lot
Rick Wilson of Rice University studied "Fiscal Attraction." He found a correlation between good looks and success. In particular, the better a person looks, the more other people trust them, and trust is a quality most leaders possess. One of his findings also showed that subjects ranked people who were smiling as more trustworthy than people with straight faces.
If you're attractive
Yale's Daniel Hamermesh conducted a study, “Beauty in the Labor Market.” He found that people with above average looks typically received premiums in pay of 5% or more, and that less attractive people "suffered a salary penalty of up to 9%." Hamermesh also writes that attractive men earn 9% more than unattractive men, and attractive women earn 4% more than unattractive women.
But not if you're too attractive
Normally, being pretty is a good thing. It's been proven time and time again that attractive people make more money. Cute babies are held and played with more than others, teachers have higher expectations in the classroom for good-looking children, and hiring decisions are made largely (but often subconsciously) on looks.
One study, Physical Attractiveness Bias in Hiring, shows that beauty can be beastly. When women apply for jobs typically handled by men, they are discriminated against. One of the researchers says, ""In these professions [such as manager of research and development, director of finance, mechanical engineer and construction supervisor], being attractive was highly detrimental to women," said Johnson. This was only the case for women. Extraordinarily attractive men weren't found to be discriminated against.
If you have hair on your head but not on your face
According to The Times, "facial hair has long been considered a potential blight on career advancement." They report the results of a survey: "60% of businessmen without beards or moustaches feel that these features are a bad sign. Some feel that the person can’t be bothered to shave and others that they are hiding something."
63% of men also report that hair loss or balding has negatively affected their careers. US News and World Report discusses how plastic surgery can boost careers, in particular hair implants. "In the corporate world, there's a lot of emphasis on image, and image goes with self-confidence," says Antonio Armani, a Beverly Hills, Calif., cosmetic surgeon who specializes in hair transplants. "I think a lot of people do invest money in improving their looks because they feel this is one way they can go up the corporate ladder."
The American Academy of Facial Plastic and Reconstructive Surgery also reported that two thirds of its members, both men and women, wanted cosmetic surgery because they wanted to "remain competitive in the workplace."
If you're a woman who wears makeup
According to TheGlassHammer, a website designed for women executives, "there is strong statistical evidence to show that women who wear make-up in business get better jobs and are promoted more quickly." And a survey reported in The Times shows that "64 per cent of directors said that women who wore make-up look more professional and 18 per cent of directors said that women who do not wear make-up “look like they can’t be bothered to make an effort”.
If you dress conservatively
Harvard Business Review writes about how dressing professionally and conservatively can advance careers: "Women, in particular, believed that dressing the part was a vital factor in attaining success: 53% of them felt aspiring female execs needed to toe a very conservative line, avoiding flashy make-up, plunging necklines, too-short or too-tight skirts, and long fingernails — exactly the sort of sartorial no-nos UBS spelled out. "Indeed, half the women surveyed and 37% of the men considered appearance and EP to be intrinsically linked; they understood that if you don't look the part of a leader, you're not likely to be given the role.
Far from imagining that appearance is a personal matter, they perceived that looking well-turned-out engenders self confidence, a trait they considered the bedrock of authentic leaders."
If you have great posture
According to Harvard Business School's study, "Power Posing: Brief Nonverbal Displays Affect Neuroendocrine Levels and Risk Tolerance," sitting in a position that oozes confidence (i.e. legs up on your desk, chest puffed out, or leaning forward) will make people deem you powerful.
Why?
It raises testosterone levels by roughly 20% and lowers the stress hormone cortisol by the same. The reverse is also true. If you slouch, cross your legs, or look weak, it works against you. Sitting powerfully for just two minutes can make a psychological difference.
According to the study, "High-power posers were more likely than low-power posers to focus on rewards— 86.36% took an offered gambling risk (only 13.63% were risk averse). In contrast, only 60% of the low-power posers took the risk (and 40% were risk averse).
Finally, high-power posers reported feeling significantly more “powerful” and “in charge.”
"I pray that this article empowers you to Get A L.I.F.E."
Saturday, February 19, 2011
Credit Scores Matter
Most of us don't need to be reminded of the importance of reviewing credit reports and fixing any errors, we know that keeping a clean and accurate credit report is important.
If you're one of the many Americans who already own your home and a car (or don't plan on buying either in the near future), you probably think that your credit score itself isn't that important. If you aren't getting a loan in the near future, why should you worry about your score? Unfortunately, your credit score is more important than you think and is being used by many institutions to help make decisions about you.
You "borrow" from a lot of institutions without explicitly borrowing money and those institutions often check your credit to decide if they want to do business with you. If you are currently renting where you live, your landlord almost certainly checked your credit history and used that to decide whether or not to rent to you.
If you have a good credit score, they probably asked for a smaller security deposit or reduced other fees. If you had a weaker score, or no score, they may have asked for more to offset the additional risk. If you're wondering what you borrowed from them, you borrowed the right to live in that home. The worst case for a landlord is to not be able to collect rent and be forced to go through the eviction process, which in some states can take many months. That's a risk they try to avoid and a credit report helps them do that.
If you're looking for a job, some employers are allowed to use your credit history to determine how safe of a candidate you are. While it's been shown that there's no relationship between a bad score and being untrustworthy, some employers, unless barred by law, are still using it to help them decide whether or not to hire a candidate. The last thing you want to do is have a missed payment cost you a job.
Those are just a few of the unexpected ways that a bad credit score can hurt you but fortunately you can do something about it. Be diligent about reviewing your credit reports and fixing any errors and inaccuracies. If you've been checking regularly and have seen no errors, keep up with it. Sometimes errors appear when you least expect them.
I've been reviewing my credit report for years and only just recently did I see a major problem (an unrelated account, which was behind on payments, appeared in my Experian report earlier this year), so stay on top of it. You can check your credit report for free at AnnualCreditReport.com.
If you're curious, there are ways for you to check your credit score for free if you're willing to sign up for some trials. I would avoid dealing with companies that aren't Fair Isaac Corporation (makers of the FICO score) or one of the three credit bureaus (Experian, Equifax, TransUnion). Fair Isaac's consumer facing company is MyFICO and you can often find plenty of MyFICO promotion codes.
"I pray that this article empowers you to Get A L.I.F.E."
If you're one of the many Americans who already own your home and a car (or don't plan on buying either in the near future), you probably think that your credit score itself isn't that important. If you aren't getting a loan in the near future, why should you worry about your score? Unfortunately, your credit score is more important than you think and is being used by many institutions to help make decisions about you.
You "borrow" from a lot of institutions without explicitly borrowing money and those institutions often check your credit to decide if they want to do business with you. If you are currently renting where you live, your landlord almost certainly checked your credit history and used that to decide whether or not to rent to you.
If you have a good credit score, they probably asked for a smaller security deposit or reduced other fees. If you had a weaker score, or no score, they may have asked for more to offset the additional risk. If you're wondering what you borrowed from them, you borrowed the right to live in that home. The worst case for a landlord is to not be able to collect rent and be forced to go through the eviction process, which in some states can take many months. That's a risk they try to avoid and a credit report helps them do that.
If you're looking for a job, some employers are allowed to use your credit history to determine how safe of a candidate you are. While it's been shown that there's no relationship between a bad score and being untrustworthy, some employers, unless barred by law, are still using it to help them decide whether or not to hire a candidate. The last thing you want to do is have a missed payment cost you a job.
Those are just a few of the unexpected ways that a bad credit score can hurt you but fortunately you can do something about it. Be diligent about reviewing your credit reports and fixing any errors and inaccuracies. If you've been checking regularly and have seen no errors, keep up with it. Sometimes errors appear when you least expect them.
I've been reviewing my credit report for years and only just recently did I see a major problem (an unrelated account, which was behind on payments, appeared in my Experian report earlier this year), so stay on top of it. You can check your credit report for free at AnnualCreditReport.com.
If you're curious, there are ways for you to check your credit score for free if you're willing to sign up for some trials. I would avoid dealing with companies that aren't Fair Isaac Corporation (makers of the FICO score) or one of the three credit bureaus (Experian, Equifax, TransUnion). Fair Isaac's consumer facing company is MyFICO and you can often find plenty of MyFICO promotion codes.
"I pray that this article empowers you to Get A L.I.F.E."
Saturday, February 12, 2011
The Digestive System
The first step in the digestive process happens before we even taste food. Just by smelling that homemade apple pie or thinking about how delicious that ripe tomato is going to be, you start salivating — and the digestive process begins in preparation for that first bite.
Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to operate. But before food can do that, it must be digested into small pieces the body can absorb and use.
About the Digestive System
Almost all animals have a tube-type digestive system in which food enters the mouth, passes through a long tube, and exits as feces (poop) through the anus. The smooth muscle in the walls of the tube-shaped digestive organs rhythmically and efficiently moves the food through the system, where it is broken down into tiny absorbable atoms and molecules.
During the process of absorption, nutrients that come from the food (including carbohydrates, proteins, fats, vitamins, and minerals) pass through channels in the intestinal wall and into the bloodstream. The blood works to distribute these nutrients to the rest of the body. The waste parts of food that the body can't use are passed out of the body as feces.
Every morsel of food we eat has to be broken down into nutrients that can be absorbed by the body, which is why it takes hours to fully digest food. In humans, protein must be broken down into amino acids, starches into simple sugars, and fats into fatty acids and glycerol. The water in our food and drink is also absorbed into the bloodstream to provide the body with the fluid it needs.
How Digestion Works
The digestive system is made up of the alimentary canal (also called the digestive tract) and the other abdominal organs that play a part in digestion, such as the liver and pancreas. The alimentary canal is the long tube of organs — including the esophagus, stomach, and intestines — that runs from the mouth to the anus. An adult's digestive tract is about 30 feet (about 9 meters) long.
Digestion begins in the mouth, well before food reaches the stomach. When we see, smell, taste, or even imagine a tasty meal, our salivary glands, which are located under the tongue and near the lower jaw, begin producing saliva. This flow of saliva is set in motion by a brain reflex that's triggered when we sense food or think about eating. In response to this sensory stimulation, the brain sends impulses through the nerves that control the salivary glands, telling them to prepare for a meal.
As the teeth tear and chop the food, saliva moistens it for easy swallowing. A digestive enzyme called amylase, which is found in saliva, starts to break down some of the carbohydrates (starches and sugars) in the food even before it leaves the mouth.
Swallowing, which is accomplished by muscle movements in the tongue and mouth, moves the food into the throat, or pharynx. The pharynx, a passageway for food and air, is about 5 inches (12.7 centimeters) long. A flexible flap of tissue called the epiglottis reflexively closes over the windpipe when we swallow to prevent choking.
From the throat, food travels down a muscular tube in the chest called the esophagus. Waves of muscle contractions called peristalsis force food down through the esophagus to the stomach. A person normally isn't aware of the movements of the esophagus, stomach, and intestine that take place as food passes through the digestive tract.
At the end of the esophagus, a muscular ring or valve called a sphincter allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus. The stomach muscles churn and mix the food with acids and enzymes, breaking it into much smaller, digestible pieces. An acidic environment is needed for the digestion that takes place in the stomach. Glands in the stomach lining produce about 3 quarts (2.8 liters) of these digestive juices each day.
Most substances in the food we eat need further digestion and must travel into the intestine before being absorbed. When it's empty, an adult's stomach has a volume of one fifth of a cup (1.6 fluid ounces), but it can expand to hold more than 8 cups (64 fluid ounces) of food after a large meal.
Role of the Intestines
By the time food is ready to leave the stomach, it has been processed into a thick liquid called chyme. A walnut-sized muscular valve at the outlet of the stomach called the pylorus keeps chyme in the stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted down into the small intestine, where digestion of food continues so the body can absorb the nutrients into the bloodstream.
The small intestine is made up of three parts:
1. the duodenum, the C-shaped first part
2. the jejunum, the coiled midsection
3. the ileum, the final section that leads into the large intestine
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi. The villi are the vehicles through which nutrients can be absorbed into the body.
The liver (located under the ribcage in the right upper part of the abdomen), the gallbladder (hidden just below the liver), and the pancreas (beneath the stomach) are not part of the alimentary canal, but these organs are essential to digestion.
The liver produces bile, which helps the body absorb fat. Bile is stored in the gallbladder until it is needed. The pancreas produces enzymes that help digest proteins, fats, and carbs. It also makes a substance that neutralizes stomach acid. These enzymes and bile travel through special channels (called ducts) directly into the small intestine, where they help to break down food. The liver also plays a major role in the handling and processing of nutrients, which are carried to the liver in the blood from the small intestine.
From the small intestine, undigested food (and some water) travels to the large intestine through a muscular ring or valve that prevents food from returning to the small intestine. By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine's main function is to remove water from the undigested matter and form solid waste that can be excreted.
The large intestine is made up of three parts:
1. The cecum is a pouch at the beginning of the large intestine that joins the small intestine to the large intestine. This transition area expands in diameter, allowing food to travel from the small intestine to the large. The appendix, a small, hollow, finger-like pouch, hangs at the end of the cecum. Doctors believe the appendix is left over from a previous time in human evolution. It no longer appears to be useful to the digestive process.
2. The colon extends from the cecum up the right side of the abdomen, across the upper abdomen, and then down the left side of the abdomen, finally connecting to the rectum. The colon has three parts: the ascending colon; the transverse colon, which absorb fluids and salts; and the descending colon, which holds the resulting waste. Bacteria in the colon help to digest the remaining food products.
3. The rectum is where feces are stored until they leave the digestive system through the anus as a bowel movement.
Digestive System Problems
Nearly everyone has a digestive problem at one time or another. Some conditions, like indigestion or mild diarrhea, are common; they result in mild discomfort and get better on their own or are easy to treat. Others, such as inflammatory bowel disease (IBD), can be ongoing and troublesome and should be discussed with a GI specialist or gastroenterologist (doctors who specialize in the digestive system).
Problems With the Esophagus
Problems affecting the esophagus may be congenital (present at birth) or noncongenital (developed after birth). Examples include:
Congenital conditions. Tracheoesophageal fistula is a connection between the esophagus and the trachea (windpipe) where there shouldn't be one. In babies with esophageal atresia, the esophagus comes to a dead end instead of connecting to the stomach. Both conditions are usually detected soon after a baby is born — sometimes even before — and require surgery to repair.
Noncongenital conditions. Esophagitis (inflammation of the esophagus) can be caused by infection, certain medications, or gastroesophageal reflux disease (GERD). With GERD, the esophageal sphincter (the valve that connects the esophagus with the stomach) doesn't work well and allows the acidic contents of the stomach to move backward up into the esophagus. GERD often can be corrected through lifestyle changes, such as dietary adjustments. Sometimes, though, it requires treatment with medication.
Problems With the Stomach and Intestines
Almost everyone has experienced diarrhea or constipation. With diarrhea, muscle contractions move the contents of the intestines along too quickly and there isn't enough time for water to be absorbed before the feces are pushed out of the body. Constipation is the opposite: The contents of the large intestines do not move along fast enough and waste materials stay in the large intestine so long that too much water is removed and the feces become hard.
Other common stomach and intestinal disorders include:
Gastrointestinal infections can be caused by viruses, by bacteria (such as Salmonella, Shigella, Campylobacter, or E. coli), or by intestinal parasites (such as amebiasis and giardiasis). Abdominal pain or cramps, diarrhea, and sometimes vomiting are the common symptoms of gastrointestinal infections. These usually go away on their own without medicines or other treatment.
Appendicitis, an inflammation of the appendix, most often affects kids and teens between 11 and 20 years old, and requires surgery to correct. The classic symptoms of appendicitis are abdominal pain, fever, loss of appetite, and vomiting.
Gastritis and peptic ulcers arise when a bacterium, Helicobacter pylori, or the chronic use of drugs or certain medications weakens the protective mucous coating of the stomach and duodenum, allowing acid to get through to the sensitive lining beneath. This can irritate and inflame the lining of the stomach (gastritis) or cause peptic ulcers, which are sores or holes in the lining of the stomach or the duodenum that cause pain or bleeding. Medications usually successfully treat these conditions.
Inflammatory bowel disease (IBD) is chronic inflammation of the intestines that affects older kids, teens, and adults. There are two major types: ulcerative colitis, which usually affects just the rectum and the large intestine; and Crohn's disease, which can affect the whole gastrointestinal tract from the mouth to the anus as well as other parts of the body. They are treated with medications and, if necessary, intravenous (IV) feedings to provide nutrition. In some cases, surgery may be necessary to remove inflamed or damaged areas of the intestine.
Celiac disease is a disorder in which the digestive system is damaged by the response of the immune system to a protein called gluten, which is found in wheat, rye, and barley and a wide range of foods, from breakfast cereal to pizza crust. People with celiac disease have difficulty digesting the nutrients from their food and may experience diarrhea, abdominal pain, bloating, exhaustion, and depression when they eat foods with gluten. Symptoms can be managed by following a gluten-free diet. Celiac disease runs in families and can become active after some sort of stress, such as surgery or a viral infection. A doctor can diagnose celiac disease with a blood test and by taking a biopsy of the small intestine.
Irritable bowel syndrome (IBS), a common intestinal disorder, affects the colon and may cause recurrent abdominal cramps, bloating, constipation, and diarrhea. There is no cure, but IBS symptoms may be treated by changing eating habits, reducing stress, and making lifestyle changes. A doctor may also prescribe medications to relieve diarrhea or constipation. No one test is used to diagnose IBS, but a doctor may identify it based on symptoms, medical history, and a physical exam.
Problems With the Pancreas, Liver, and Gallbladder Conditions affecting the pancreas, liver, and gallbladder often affect the ability of these organs to produce enzymes and other substances that aid in digestion. Examples include:
Cystic fibrosis is a chronic, inherited illness where the production of abnormally thick mucus blocks the ducts or passageways in the pancreas and prevents its digestive juices from entering the intestines, making it difficult to properly digest proteins and fats. This causes important nutrients to pass out of the body unused. To help manage their digestive problems, people with cystic fibrosis can take digestive enzymes and nutritional supplements.
Hepatitis, a condition with many different causes, is when the liver becomes inflamed and may lose its ability to function. Viral hepatitis, such as hepatitis A, B, or C, is highly contagious. Mild cases of hepatitis A can be treated at home; however, serious cases involving liver damage may require hospitalization.
The gallbladder can develop gallstones and become inflamed — a condition called cholecystitis. Although gallbladder conditions are uncommon in kids and teens, they can occur in those who have sickle cell anemia or are being treated with certain long-term medications.
Keeping Digestion on Track
The kinds and amounts of food a person eats and how the digestive system processes that food play key roles in maintaining good health. Eating a healthy diet is the best way to prevent common digestive problems.
"I pray that this article empowers you to Get A L.I.F.E."
Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to operate. But before food can do that, it must be digested into small pieces the body can absorb and use.
About the Digestive System
Almost all animals have a tube-type digestive system in which food enters the mouth, passes through a long tube, and exits as feces (poop) through the anus. The smooth muscle in the walls of the tube-shaped digestive organs rhythmically and efficiently moves the food through the system, where it is broken down into tiny absorbable atoms and molecules.
During the process of absorption, nutrients that come from the food (including carbohydrates, proteins, fats, vitamins, and minerals) pass through channels in the intestinal wall and into the bloodstream. The blood works to distribute these nutrients to the rest of the body. The waste parts of food that the body can't use are passed out of the body as feces.
Every morsel of food we eat has to be broken down into nutrients that can be absorbed by the body, which is why it takes hours to fully digest food. In humans, protein must be broken down into amino acids, starches into simple sugars, and fats into fatty acids and glycerol. The water in our food and drink is also absorbed into the bloodstream to provide the body with the fluid it needs.
How Digestion Works
The digestive system is made up of the alimentary canal (also called the digestive tract) and the other abdominal organs that play a part in digestion, such as the liver and pancreas. The alimentary canal is the long tube of organs — including the esophagus, stomach, and intestines — that runs from the mouth to the anus. An adult's digestive tract is about 30 feet (about 9 meters) long.
Digestion begins in the mouth, well before food reaches the stomach. When we see, smell, taste, or even imagine a tasty meal, our salivary glands, which are located under the tongue and near the lower jaw, begin producing saliva. This flow of saliva is set in motion by a brain reflex that's triggered when we sense food or think about eating. In response to this sensory stimulation, the brain sends impulses through the nerves that control the salivary glands, telling them to prepare for a meal.
As the teeth tear and chop the food, saliva moistens it for easy swallowing. A digestive enzyme called amylase, which is found in saliva, starts to break down some of the carbohydrates (starches and sugars) in the food even before it leaves the mouth.
Swallowing, which is accomplished by muscle movements in the tongue and mouth, moves the food into the throat, or pharynx. The pharynx, a passageway for food and air, is about 5 inches (12.7 centimeters) long. A flexible flap of tissue called the epiglottis reflexively closes over the windpipe when we swallow to prevent choking.
From the throat, food travels down a muscular tube in the chest called the esophagus. Waves of muscle contractions called peristalsis force food down through the esophagus to the stomach. A person normally isn't aware of the movements of the esophagus, stomach, and intestine that take place as food passes through the digestive tract.
At the end of the esophagus, a muscular ring or valve called a sphincter allows food to enter the stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus. The stomach muscles churn and mix the food with acids and enzymes, breaking it into much smaller, digestible pieces. An acidic environment is needed for the digestion that takes place in the stomach. Glands in the stomach lining produce about 3 quarts (2.8 liters) of these digestive juices each day.
Most substances in the food we eat need further digestion and must travel into the intestine before being absorbed. When it's empty, an adult's stomach has a volume of one fifth of a cup (1.6 fluid ounces), but it can expand to hold more than 8 cups (64 fluid ounces) of food after a large meal.
Role of the Intestines
By the time food is ready to leave the stomach, it has been processed into a thick liquid called chyme. A walnut-sized muscular valve at the outlet of the stomach called the pylorus keeps chyme in the stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted down into the small intestine, where digestion of food continues so the body can absorb the nutrients into the bloodstream.
The small intestine is made up of three parts:
1. the duodenum, the C-shaped first part
2. the jejunum, the coiled midsection
3. the ileum, the final section that leads into the large intestine
The inner wall of the small intestine is covered with millions of microscopic, finger-like projections called villi. The villi are the vehicles through which nutrients can be absorbed into the body.
The liver (located under the ribcage in the right upper part of the abdomen), the gallbladder (hidden just below the liver), and the pancreas (beneath the stomach) are not part of the alimentary canal, but these organs are essential to digestion.
The liver produces bile, which helps the body absorb fat. Bile is stored in the gallbladder until it is needed. The pancreas produces enzymes that help digest proteins, fats, and carbs. It also makes a substance that neutralizes stomach acid. These enzymes and bile travel through special channels (called ducts) directly into the small intestine, where they help to break down food. The liver also plays a major role in the handling and processing of nutrients, which are carried to the liver in the blood from the small intestine.
From the small intestine, undigested food (and some water) travels to the large intestine through a muscular ring or valve that prevents food from returning to the small intestine. By the time food reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine's main function is to remove water from the undigested matter and form solid waste that can be excreted.
The large intestine is made up of three parts:
1. The cecum is a pouch at the beginning of the large intestine that joins the small intestine to the large intestine. This transition area expands in diameter, allowing food to travel from the small intestine to the large. The appendix, a small, hollow, finger-like pouch, hangs at the end of the cecum. Doctors believe the appendix is left over from a previous time in human evolution. It no longer appears to be useful to the digestive process.
2. The colon extends from the cecum up the right side of the abdomen, across the upper abdomen, and then down the left side of the abdomen, finally connecting to the rectum. The colon has three parts: the ascending colon; the transverse colon, which absorb fluids and salts; and the descending colon, which holds the resulting waste. Bacteria in the colon help to digest the remaining food products.
3. The rectum is where feces are stored until they leave the digestive system through the anus as a bowel movement.
Digestive System Problems
Nearly everyone has a digestive problem at one time or another. Some conditions, like indigestion or mild diarrhea, are common; they result in mild discomfort and get better on their own or are easy to treat. Others, such as inflammatory bowel disease (IBD), can be ongoing and troublesome and should be discussed with a GI specialist or gastroenterologist (doctors who specialize in the digestive system).
Problems With the Esophagus
Problems affecting the esophagus may be congenital (present at birth) or noncongenital (developed after birth). Examples include:
Congenital conditions. Tracheoesophageal fistula is a connection between the esophagus and the trachea (windpipe) where there shouldn't be one. In babies with esophageal atresia, the esophagus comes to a dead end instead of connecting to the stomach. Both conditions are usually detected soon after a baby is born — sometimes even before — and require surgery to repair.
Noncongenital conditions. Esophagitis (inflammation of the esophagus) can be caused by infection, certain medications, or gastroesophageal reflux disease (GERD). With GERD, the esophageal sphincter (the valve that connects the esophagus with the stomach) doesn't work well and allows the acidic contents of the stomach to move backward up into the esophagus. GERD often can be corrected through lifestyle changes, such as dietary adjustments. Sometimes, though, it requires treatment with medication.
Problems With the Stomach and Intestines
Almost everyone has experienced diarrhea or constipation. With diarrhea, muscle contractions move the contents of the intestines along too quickly and there isn't enough time for water to be absorbed before the feces are pushed out of the body. Constipation is the opposite: The contents of the large intestines do not move along fast enough and waste materials stay in the large intestine so long that too much water is removed and the feces become hard.
Other common stomach and intestinal disorders include:
Gastrointestinal infections can be caused by viruses, by bacteria (such as Salmonella, Shigella, Campylobacter, or E. coli), or by intestinal parasites (such as amebiasis and giardiasis). Abdominal pain or cramps, diarrhea, and sometimes vomiting are the common symptoms of gastrointestinal infections. These usually go away on their own without medicines or other treatment.
Appendicitis, an inflammation of the appendix, most often affects kids and teens between 11 and 20 years old, and requires surgery to correct. The classic symptoms of appendicitis are abdominal pain, fever, loss of appetite, and vomiting.
Gastritis and peptic ulcers arise when a bacterium, Helicobacter pylori, or the chronic use of drugs or certain medications weakens the protective mucous coating of the stomach and duodenum, allowing acid to get through to the sensitive lining beneath. This can irritate and inflame the lining of the stomach (gastritis) or cause peptic ulcers, which are sores or holes in the lining of the stomach or the duodenum that cause pain or bleeding. Medications usually successfully treat these conditions.
Inflammatory bowel disease (IBD) is chronic inflammation of the intestines that affects older kids, teens, and adults. There are two major types: ulcerative colitis, which usually affects just the rectum and the large intestine; and Crohn's disease, which can affect the whole gastrointestinal tract from the mouth to the anus as well as other parts of the body. They are treated with medications and, if necessary, intravenous (IV) feedings to provide nutrition. In some cases, surgery may be necessary to remove inflamed or damaged areas of the intestine.
Celiac disease is a disorder in which the digestive system is damaged by the response of the immune system to a protein called gluten, which is found in wheat, rye, and barley and a wide range of foods, from breakfast cereal to pizza crust. People with celiac disease have difficulty digesting the nutrients from their food and may experience diarrhea, abdominal pain, bloating, exhaustion, and depression when they eat foods with gluten. Symptoms can be managed by following a gluten-free diet. Celiac disease runs in families and can become active after some sort of stress, such as surgery or a viral infection. A doctor can diagnose celiac disease with a blood test and by taking a biopsy of the small intestine.
Irritable bowel syndrome (IBS), a common intestinal disorder, affects the colon and may cause recurrent abdominal cramps, bloating, constipation, and diarrhea. There is no cure, but IBS symptoms may be treated by changing eating habits, reducing stress, and making lifestyle changes. A doctor may also prescribe medications to relieve diarrhea or constipation. No one test is used to diagnose IBS, but a doctor may identify it based on symptoms, medical history, and a physical exam.
Problems With the Pancreas, Liver, and Gallbladder Conditions affecting the pancreas, liver, and gallbladder often affect the ability of these organs to produce enzymes and other substances that aid in digestion. Examples include:
Cystic fibrosis is a chronic, inherited illness where the production of abnormally thick mucus blocks the ducts or passageways in the pancreas and prevents its digestive juices from entering the intestines, making it difficult to properly digest proteins and fats. This causes important nutrients to pass out of the body unused. To help manage their digestive problems, people with cystic fibrosis can take digestive enzymes and nutritional supplements.
Hepatitis, a condition with many different causes, is when the liver becomes inflamed and may lose its ability to function. Viral hepatitis, such as hepatitis A, B, or C, is highly contagious. Mild cases of hepatitis A can be treated at home; however, serious cases involving liver damage may require hospitalization.
The gallbladder can develop gallstones and become inflamed — a condition called cholecystitis. Although gallbladder conditions are uncommon in kids and teens, they can occur in those who have sickle cell anemia or are being treated with certain long-term medications.
Keeping Digestion on Track
The kinds and amounts of food a person eats and how the digestive system processes that food play key roles in maintaining good health. Eating a healthy diet is the best way to prevent common digestive problems.
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