HIV and AIDS
Urinary System Physiology
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 process is called 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 pronounced: 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. They are caused by prostaglandins, chemicals in the body that makes 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. If a female and male have sex within several days of the female's ovulation egg release , fertilization can occur. When the male ejaculates which is when semen leaves a man's penis , between 0.
Between 75 and 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 multi-celled blastocyst pronounced: 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 pronounced: 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 pronounced: 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 pronounced: The fetus receives oxygen and nourishment from the mother's blood via the placenta pronounced: The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mother's body.
Pregnancy lasts an average of 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 pronounced: The urethra is the tube through which urine passes from the bladder to the exterior of the body.
The female urethra is around 2 inches long and ends inferior to the clitoris and superior to the vaginal opening. In males, the urethra is around 8 to 10 inches long and ends at the tip of the penis. The urethra is also an organ of the male reproductive system as it carries sperm out of the body through the penis. The flow of urine through the urethra is controlled by the internal and external urethral sphincter muscles. The internal urethral sphincter is made of smooth muscle and opens involuntarily when the bladder reaches a certain set level of distention.
The opening of the internal sphincter results in the sensation of needing to urinate. The external urethral sphincter is made of skeletal muscle and may be opened to allow urine to pass through the urethra or may be held closed to delay urination. The kidneys maintain the homeostasis of several important internal conditions by controlling the excretion of substances out of the body.
The kidney can control the excretion of potassium, sodium, calcium, magnesium, phosphate, and chloride ions into urine. In cases where these ions reach a higher than normal concentration, the kidneys can increase their excretion out of the body to return them to a normal level. Conversely, the kidneys can conserve these ions when they are present in lower than normal levels by allowing the ions to be reabsorbed into the blood during filtration.
See more about ions. The kidneys also conserve bicarbonate ions, which act as important pH buffers in the blood. The cells of the body need to grow in an isotonic environment in order to maintain their fluid and electrolyte balance. When a person consumes a large amount of water, the kidneys reduce their reabsorption of water to allow the excess water to be excreted in urine. This results in the production of dilute, watery urine.
In the case of the body being dehydrated, the kidneys reabsorb as much water as possible back into the blood to produce highly concentrated urine full of excreted ions and wastes. The changes in excretion of water are controlled by antidiuretic hormone ADH.
ADH is produced in the hypothalamus and released by the posterior pituitary gland to help the body retain water. When blood pressure is elevated, the kidneys can help to reduce blood pressure by reducing the volume of blood in the body.
The kidneys are able to reduce blood volume by reducing the reabsorption of water into the blood and producing watery, dilute urine. When blood pressure becomes too low, the kidneys can produce the enzyme renin to constrict blood vessels and produce concentrated urine, which allows more water to remain in the blood. Inside each kidney are around a million tiny structures called nephrons. The nephron is the functional unit of the kidney that filters blood to produce urine.
Arterioles in the kidneys deliver blood to a bundle of capillaries surrounded by a capsule called a glomerulus. Problems caused by uterine fibroids can include heavy or painful menstrual bleeding, frequent urination, lower back pain, pain during sexual intercourse or reproductive problems, such as miscarriage or infertility.
The most common forms of treatment for uterine fibroids include pain medication and surgery. If your ovaries stop producing eggs before you are 40 years of age, you can be diagnosed with premature ovarian failure. Certain women with this condition may still experience irregular menstrual cycles, making this ovarian problem distinct from menopause. Symptoms of premature ovarian failure include mood alterations, hot flashes, difficulty concentrating, vaginal drying and decreased libido.
Though women with this condition can still become pregnant, it may be difficult to do. If you have premature ovarian failure, your doctor may recommend estrogen replacement therapy to help you have a regular menstrual cycle. Polycystic ovary syndrome PCOS occurs when your ovaries produce increased levels of a specific type of hormone androgens. Increased androgen hormone levels within the body can negatively affect the normal ovulation process and cause fluid-filled cysts to form on the ovaries.
PCOS prevents ovarian egg release during the menstrual cycle, which causes infertility in women with this condition. Additional symptoms of PCOS include pelvic pain, acne, oily skin, hair loss or excessive hair growth on the body or face. Currently, there is no cure for PCOS but hormone therapy can help regulate your menstrual cycle or clear up your skin.
If you develop an infection or excessive inflammation of the vagina or vulva tissues, you can be diagnosed with a common condition called vulvovaginitis.