THE REPRODUCTIVE SYSTEM and ENDOCRINE SYSTEM.docx

THE REPRODUCTIVE SYSTEM The reproductive system is a collection of organs and a network of hormone production that work together to create life. The male reproductive system includes the testes (which produce sperm), penis, epididymis, vas deferens, ejaculatory ducts and urethra. The female repro...

THE REPRODUCTIVE SYSTEM The reproductive system is a collection of organs and a network of hormone production that work together to create life. The male reproductive system includes the testes (which produce sperm), penis, epididymis, vas deferens, ejaculatory ducts and urethra. The female reproductive system consists of the ovaries (which produce eggs or oocytes), fallopian tubes, uterus, cervix, vagina and vulva. Both the male and female reproductive systems must be functioning properly for a couple to conceive naturally. A problem with the structure or function of either reproductive system can cause infertility. a network of hormone production in men and women enables a man to impregnate a woman who gives birth to a child. During conception, a sperm cell from the man fuses with an egg cell in the woman, creating a fertilized egg (embryo) that implants and grows in the uterus during pregnancy. FEMALE REPRODUCTIVE SYSTEM The female reproductive system is designed to: Produce the eggs necessary for reproduction, called the ova (ovum is singular for one egg) or oocytes. Incubate and nourish a fertilized egg until it is fully developed. Produce female sex hormones that maintain the reproductive cycle. Hormones made in the hypothalamus, pituitary, and ovary work together in a complicated way to control the menstrual cycle. FSH, which is released by the pituitary gland, tells the ovarian follicles to start growing and maturing. Follicles are structures in the ovary that look like sacs and hold eggs. Cells inside the follicle make estrogen as the egg and follicle grow. Follicle cells make a different hormone, inhibin, which goes back to the hypothalamus and pituitary to lower the amount of FSH that is released. According to FSH, the production of estrogen keeps going up as the follicle matures and gets bigger. When the follicle is fully grown, it makes the most estrogen. This causes the pituitary gland to release LH very quickly. When the ovaries make estrogen and LH, they work together to help the egg mature. Ovulation, the release of a mature egg from one of the follicles in the ovary, is also set off by LH. The follicle changes into a different structure called the corpus luteum after ovulation. This structure makes progesterone. Progesterone thickens the endometrium, the lining of the uterus, so it's ready for the embryo to implant. For implantation and pregnancy to happen, progesterone is needed. If implantation doesn't happen, the endometrium will break down during menstruation and be lost. The female reproductive organs include: Ovaries — The ovaries are two small, oval-shaped glands located on either side of the uterus. They are home to the female sex cells, called eggs, and they also produce oestrogen, the female sex hormone. Fallopian tubes — The fallopian tubes are narrow tunnels for a fertilized egg to make its way down to the uterus. Damage or blockage to the fallopian tubes — called tubal disease — can sometimes cause fertility problems. Uterus — The uterus is a hollow, pear-shaped organ located in a woman’s lower abdomen, between the bladder and the rectum. It is also called the “womb” and holds the foetus during pregnancy. Each month, the uterus develops a lining (the endometrium) that is rich in nutrients. The reproductive purpose of this lining is to provide nourishment for a developing foetus. Uterine abnormalities, such as fibroids or endometriosis, may cause infertility by interfering with egg fertilization or embryo implantation and development. Cervix — The cervix is the lower, narrow part of the uterus, located between the bladder and rectum. It forms a canal that opens to the vagina. Often called the neck or entrance to the womb, the cervix lets menstrual blood out and semen into the uterus. Growths in the cervix called polyps can sometimes affect the fertilization or embryo growth process. Vagina — The vagina, also known as the birth canal, joins the cervix (the lower part of uterus) to the outside of the body. Vulva — This is the external portion of the female genital organs. MALE REPRODUCTIVE SYSTEM The male reproductive system performs the following functions: Produces, maintains and transports sperm (the male reproductive cells) and protective fluid (semen) Discharges sperm within the female reproductive tract during sex Produces and secretes male sex hormones responsible for maintaining the male reproductive system. In men, FSH from the pituitary gland stimulates the testes to produce sperm by a process known as spermatogenesis. LH from the pituitary gland signals the testes to produce testosterone, which enhances sperm maturation. Testosterone is the primary male sex hormone. Unlike in the female reproductive system, most male reproductive organs are not located internally. They include: Penis — The penis is made up of two parts, the shaft and the head. The urethral opening at the tip of the penis delivers sperm into the vagina during sexual intercourse. Scrotum — The scrotum is the sac-like organ hanging behind and below the penis. It contains the testicles (also called testes), as well as many nerves and blood vessels. Testicles (testes) — The testes (oval organs that lie in the scrotum) are the primary male reproductive organ and are responsible for testosterone and sperm production. Epididymis — The epididymis is a C-shaped tube that rests on the backside of each testicle. It transports and stores sperm cells that are produced in the testes. The epididymis also brings the sperm to maturity, since the sperm emerging from the testes are immature and incapable of fertilization. During sexual arousal, contractions force the sperm into the vas deferens. Ductus (vas) deferens — The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports mature sperm to the urethra, the tube that carries urine or sperm outside of the body, in preparation for ejaculation. Ejaculatory ducts — These are formed by the fusion of the vas deferens and the seminal vesicles. The ejaculatory ducts empty into the urethra. Urethra — The urethra is the tube that carries urine from the bladder to outside of the body. In males, it has the additional function of ejaculating semen when the man reaches sexual climax. When the penis is erect during sex, the flow of urine is blocked from the urethra, allowing only semen to be ejaculated at climax. Other glands — Several glands produce semen or fluid in support of the reproductive process. The seminal vesicle produces fructose that provides energy to the sperm as they seek an egg. The prostate gland also produces a fluid that helps the sperm move more quickly through the female reproductive system. Another set of glands called bulbourethral, or sometimes Cowper’s glands, makes a fluid for protecting the sperm on its way through the urethra. THE ENDOCRINE SYSTEM The endocrine system is made up of glands that make hormones. Hormones are the body's chemical messengers. They carry information and instructions from one set of cells to another. The endocrine system influences almost every cell, organ, and function of our bodies. Hormones enter the bloodstream from endocrine glands. Hormones can now get to cells in other parts of the body. Hormones that are found in the endocrine system help control our mood, our bones and muscles, our metabolism, and cell reproduction. How much of each hormone is released is controlled by the endocrine system. This might depend on how much of certain hormones or other substances, like calcium, are already in the blood. Stress, an infection, and changes in the balance of minerals and fluids in the blood are just a few of the things that can change hormone levels. Any hormone that is too high or too low can hurt the body. A lot of these problems can be fixed with medicine. PARTS OF THE ENDOCRINE SYSTEM While many parts of the body make hormones, the major glands that make up the endocrine system are the: hypothalamus pituitary thyroid parathyroids adrenals pineal body the ovaries the testes The pancreas is part of the endocrine system and the digestive system. That's because it secretes hormones into the bloodstream and makes and secretes enzymes into the digestive tract. Hypothalamus: The hypothalamus is in the lower central part of the brain. It links the endocrine system and nervous system. Nerve cells in the hypothalamus make chemicals that control the release of hormones secreted from the pituitary gland. The hypothalamus gathers information sensed by the brain (such as the surrounding temperature, light exposure, and feelings) and sends it to the pituitary. This information influences the hormones that the pituitary makes and releases. Pituitary: The pituitary gland is at the base of the brain and is no bigger than a pea. Despite its small size, the pituitary is often called the "master gland." The hormones it makes control many other endocrine glands. The pituitary gland makes many hormones, such as: 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 make thyroid hormones. corticotropin, which stimulates the adrenal gland to make certain hormones. antidiuretic hormone, which helps control body water balance through its effect on the kidneys. oxytocin, which triggers the contractions of the uterus that happen during labour. The pituitary also secretes endorphins, chemicals that act on the nervous system and reduce feelings of pain. The pituitary also secretes hormones that signal the reproductive organs to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women. Thyroid: The thyroid is in the front part of the lower neck. It's shaped like a bow tie or butterfly. It makes the thyroid hormones thyroxine and triiodothyronine. These hormones control the rate at which cells burn fuels from food to make energy. The more thyroid hormone there is in the bloodstream, the faster chemical reactions happen in the body. Thyroid hormones are important because they help kids' and teens' bones grow and develop, and they also play a role in the development of the brain and nervous system. Parathyroids: Attached to the thyroid are four tiny glands that work together called the parathyroids. They release parathyroid hormone, which controls the level of calcium in the blood with the help of calcitonin, which the thyroid makes. Adrenal Glands: These two triangular adrenal glands sit on top of each kidney. The adrenal glands have two parts, each of which makes a set of hormones and has a different function: The outer part is the adrenal cortex. It makes hormones called corticosteroids that help control 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 is the adrenal medulla. It makes catecholamines, such as epinephrine. Also called adrenaline, epinephrine increases blood pressure and heart rate when the body is under stress. Pineal: The pineal body, also called the pineal gland, is in the middle of the brain. It secretes melatonin, a hormone that may help regulate when you sleep at night and when you wake in the morning. Reproductive Glands: The gonads are the main source of sex hormones. Most people don't realize it, but both guys and girls have gonads. In guys the male gonads, or testes, are in the scrotum. They secrete hormones called androgens, the most important of which is testosterone. These hormones tell a guy's body when it's time to make the changes associated with puberty, like penis and height growth, deepening voice, and growth in facial and pubic hair. Working with hormones from the pituitary gland, testosterone also tells a guy's body when it's time to make sperm in the testes. A girls gonads, the ovaries, are in her pelvis. They make eggs and secrete the female hormones oestrogen and progesterone. Oestrogen is involved when a girl starts puberty. During puberty, a girl will have breast growth, start to accumulate body fat around the hips and thighs and have a growth spurt. Oestrogen and progesterone are also involved in the regulation of a girl's menstrual cycle. These hormones also play a role in pregnancy. Pancreas: The pancreas makes insulin and glucagon, which are hormones that control the level of glucose, or sugar, in the blood. Insulin helps keep the body supplied with stores of energy. The body uses this stored energy for exercise and activity, and it also helps organs work as they should.