The Reproductive System Outline free essay sample

The Reproductive system The gonads or primary sex organs: testes in men, and ovaries in women. a. Produce sex cells or gametes, and secrete sex hormones Male and female reproductive systems are different. Sex hormones play vital roles both in the development and function of the reproductive organs. Anatomy of the male reproductive system A. Testes Plum-sized and approx. 4cm long and 2. 5cm wide Fibrous connective tissue capsules, te tunica albuginea surrounds each testis. Each lobule contains one to four tightly coiled seminiferous tubules. . The seminiferous tubules of each lobe empty sperm into another set of tubules, the rete testis, located at one side of the testis. Sperm travel through the rete testis to enter the first part of the duct system, the epididymis, which hugs the external surface of the testis. The interstitial cells produce androgens-the most important of which testosterone. Thus sperm-producing and hormone producing functions of the testes are carried out by compl etely different cell populations. B. Duct System a. Epididymis 1. The cup shaped epididymis is a highly coiled tube about 6m long that caps the superior part of the testis and then runs down its posterolateral side. 2. It’s the first part of the male duct system and provides a temporary home for immature sperm. 3. The sperm travel this long tube that takes about 20 days to mature, gaining the ablility to swim. 4. When the male is sexually stimulated, he ejaculates, the walls of the epididymis contract to expel the sperm into the next part of the duct system, the ductus deferens. b. Ductus Deferens 1. This is also often referred to as the vas deferens. . It runs upward from the epididymis through the inguinal canal to the pelvic cavity and arches over the superior aspect of the urinary bladder. It then loops medially over the ureter and descends along the posterior bladder wall. 3. This tube is enclosed, along with blood vessels and nerves, in a connective tissue sheath called the spermatic cord. a. This travels upward through the inguinal ca nal. 4. The end of the ductus deferens expands at the apulla and then empties into the ejaculatory duct. b. The ejaculatory duct passes through the prostate gland to merge with the urethra. . The main function is to propel live sperm from their storage sites, epididymis and distal part of the ductus deferens into the urethra. 6. When ejaculation occurs, the thick layers of smooth muscle in its walls create peristaltic waves that rapidly squeeze sperm forward. 7. Part of the ductus deferens lies in the scrotum, which hangs outside the body. c. Urethra 1. It extends from the base of the urinary bladder to the tip of the penis, is the terminal part of the male duct system. 2. 3 named regions: prostatic urethra, membranous, spongy (penile) urethra. 3. The male urethra carries both sperm and urine to the body exterior. * ? Urine and sperm never pass at the same time. C. Accessory Glands and Semen d. Seminal Vesicles 1. Located at the base of the bladder, produce about 60% of seminal fluid, the fluid volume of semen. 2. Their thick, yellowish secretion is rich in sugar, vitamin C, prostaglandins, and other substances, which nourish and activate the sperm passing through the tract. 3. Sperm and seminal fluid enter the urethra together during ejaculation. * b. Prostate 1. A single doughnut shaped gland about the size of a peach pit. . Prostate gland secretion is a milky fluid that plays a role in activating sperm. 3. During ejaculation, the fluid enters the urethra though several small ducts. * c. Bulbourethral Glands 1. Tiny pea-sized glands inferior to the prostate gland 2. They produce a thick, clear mucous that drains into the penile urethra. a. This secretion is the first to pass down the urethra when a man becomes sexually excit ed. It cleanses the urethra, and serves as a lubricant during sexual intercourse. * d. Semen 1. A milky white, somewhat sticky mix of sperm and accessory gland secretions. 2. It acts as a transport medium for nutrients chemicals that protect sperm aid their movement. 3. The alkalinity of the semen helps neutralize the acidic environment of the female’s vagina, protecting the sperm. 4. It also contains seminalplasmin- an antibiotic chemical that destroys certain bacteria- the hormone relaxin, certain enzymes that enhance sperm motility, and substances that inhibit an immune response in the female reproductive tract. 5. During ejaculation 2-5 ml of semen are released, but there are between 50-150 million sperm in each ml. * D. External Genitalia 1. Includes: scrotum, and the penis . The scrotum is a divided sac of skin that hangs outside the abdominal cavity, between the legs and at the root of the penis. 3. Provides testes with a temp that is below body temp. a. Viable sperm cannot be produced at normal body temp. 4. The penis is designed to deliver sperm into the female reproductive tract. 5. The skin covered penis consists of a shaft, which ends in an enlarged tip, the glands penis. 6. The skin covering the penis is loose, and it folds downward to form a cuff of skin, the prepuce, or foreskin. 7. Erectile tissue: a spongy tissue that fills with blood during sexual excitement. . Causes penis to become larger and rigid. c. This event is called an erection, helps the penis serve as a penetrating organ to deliver the semen into the female’s reproductive tract. Male Reproductive Functions * 1. The chief role is to produce sperm and the hormone testosterone. A. Spermatogenesis 1. The production of sperm a. It begins at puberty and continues throughout life. 2. The process is begun by primitive stem cells called Spermatogonia. b. They go through rapid mitotic divisions to build up the stem cell line. 3. During puberty, follicle stimulating hormone is secreted in increasing mounts by the anterior pituitary gland. 4. In spermatogenesis, the gametes are called spermatids 5. The last stage of sperm development is called Spermi ogenesis. 6. The head of the sperm contains the DNA 7. Anterior to the helmet-like acrosome, which is produced by the Golgi apparatus and is similar to a large lysosome. 8. The entire process of spermatogenesis, from the formation of primary spermatocyte to release of immature sperm in the tubule lumen, takes 64 to 72 days. B. Testosterone 1. The most important hormonal product of the testes. 2. The interstitial cells are being activated by luteinizing hormone (LH) 3. It stimulates the adolescent growth spurt, prods his reproductive organs to develop to their adult size, underlies the sex drive, and causes the secondary male sex characteristics to appear. 4. Secondary sex characteristics: features introduced in nonreproductive organs by sex hormones. Ex: deepening of voice, increased hair growth, more muscle mass. Anatomy of the Female Reproductive System * 1. Ovaries: the primary female reproductive organs. * 2. The other organs of the reproductive system serve as accessory structures to transport, nurture, or otherwise serve the needs of the reproductive cells and/or the developing fetus. A. Ovaries 1. The paired ovaries are shaped like almonds but are nearly twice as large. 2. The many tiny sac like structures inside are called ovarian follicles. 3. Oocyte: an immature egg cell 4. As the egg begins to develop within the follicle enlarges and develops a fluid filled central region called an antrum. 5. In the event of ovulation the egg is released from the follicle. 6. Ovulation usually occurs every 28 days, but it could occur more or less frequently. 7. The ovaries are secured to the lateral walls of the pelvis by the suspensory ligaments. B. Duct system 1. The uterine tubes, uterus, and vagina form the duct system. * a. Uterine (fallopian) tubes 1. Initial point of the duct system. 2. They receive the ovulated oocyte and provide a site for fertilization. 3. About 10cm long, and extends medially from an ovary to empty into the superior region of the uterus. 4. The distal end of each uterine tube expands as the funnel-shaped infundibulum, which has finger like projections called fimbriae. 5. The fimbriae wave to create fluid currents that act to carry the oocyte into the uterine tube, where it begins the journey toward the uterus. . Because the journey to the uterus takes 3 to 4 days and the oocyte is viable for up to 24 hours after ovulation. 7. The usual site for fertilization * b. Uterus 1. Located in the pelvis between the urinary bladder and the rectum 2. A hollow organ that functions to receive, retain, and nourish a fertilized egg. 3. The major portion of the uterus is referred to as the body. The superior rounded region above the entrance of the uterine tubes is the fundus, and its narrow outlet, which protrudes into the vagina below, is the cervix. 4. There are 3 layers: endometrium, myometrium, and the perimetrium. * c. Vagina 1. A thin walled tube 8 to 10 cm long. Lies between the bladder and the rectum and extends from the cervix to the body exterior. 2. It receives the penis during sexual intercourse 3. The distal end of the vagina is partially closed by a thin fold of the mucosa called the hymen. a. The hymen is usually ruptured during penetration for the first time and it usually bleeds. b. Sometimes it will break before during sports, tampon use, or a physical examination. c. In some rare cases it has to be cut surgically. C. External Genitalia (vulva) 1. Includes: mons pubis, labia, clitoris, urethral and vaginal orifices, and greater vestibular glands. 2. The mons pubis is a fatty, rounded area overlying the pubic symphasis. b. After puberty this area is covered in hair. 1. The labia majora: two elongated hair-covered skin folds that enclose two delicate, hair-free folds, the labia minora. 2. The greater vestibular glands are mucous producing glands that flan the vagina. 3. The clitoris is a small, protruding structure that corresponds to the male penis. Female Reproductive Functions and Cycles A. Oogenesis and the ovarian cycle 1. The period in which a women’s reproductive capability gradually declines and then finally ends is called menopause. 2. Oogenesis: the process in which gametes are produced. 3. In the developing female fetus, oogonia, the female stem cells, multiply rapidly to increase their number, and then their daughter cells, primary oocytes. 4. The ovarian cycle is the changes that occur monthly in the ovary 5. At puberty there may be around 250,000 oocytes and each month one should be released but in some women more are released. . The larger cell is a secondary oocyte and the tiny cell is a polar body. 7. When ovulation occurs some women experience low abdomen pain; cramps. 8. If the ovulated secondary oocyte is penetrated by a sperm in one of the uterine tubes, the oocyte undergoes the second meiotic division that produces another polar body and an ovum. B. Uterine (menstrual) cycle 1. The events of this changes that the endometrium, or mucosa of th e uterus, goes through month after month as it responds to changes in the levels of ovarian hormones in the blood. 2. There are three stages of the menstrual cycle a. Day 1-5: Menstrual phase b. Day 6-14: Proliferative phase c. Day 15-28: Secretory phase 3. Some menstrual cycles can be as short as 21 days and as long as 40 day Events of Embryonic and fetal development 1. An oocyte is fertilizable for up to 24 hours after release; sperm are viable within the female reproductive tract for up to 48 hours. Hundreds of sperm must release their acrosomal enzymes to break down the egg’s plasma membrane 2. The early stage of embryonic development when the cell is dividing is called cleavage. . Cleavage provides a large number of cells to serve as building blocks for constructing the embryo. 4. The chorionic villi combine to form the placenta. a. Once the placenta has formed, the plate-like embryonic body, now surrounded by a fluid-filled sac called the amnion, is attached to the placenta by a blood vessel-containing stalk of tissue, the umbilical cord. b. The placenta serves respiratory, nutritive, a nd excretory needs of the embryo and produces hormones of pregnancy. 5. At week 9 the embryo is now referred to as a fetus 6. By approx. 70 days after fertilization the fetus is said to be full term and is ready to be born. 7. A pregnant woman has increased respiratory, circulatory, and urinary demands placed on her system by the developing fetus. Good nutrition is necessary to produce a healthy baby. 8. Childbirth (parturition) includes a series of events called labor. It is initiated by several but most importantly by rising levels of oxytocin and prostaglandins, which promote vigorous uterine contractions. 9. There are 3 stages of labor are dilation, expulsion, and placental. Developmental Aspects of the Reproductive System . Puberty: the period of life generally between ages of 10 and 15 2. Reproductive system structures of males and females are identical during early development. a. Gonads begin to develop in the 8th week. b. The presence or absence of testosterone determines w hether male or female accessory reproductive organs are formed. 3. Important congenital defects result from abnormal separation of sex chromosomes during sex cell formation. 4. The reproductive system is inactive during childhood. c. Reproductive organs mature and become functional for childbearing at puberty. . The first menstrual period, called menarche, usually occurs about 2years later. 6. Common reproductive problems during young adulthood are infections of the reproductive tract. d. Females: neoplasms of breast and cervix are major threats e. Males: prostate cancer is the most common reproductive system cancer seen in men. 7. During menopause, female reproductive capabilities end, and reproductive organs begin to atrophy. f. Hot flashes and mood changes may occur. g. Reproductive capacity does not appear to decline significantly in aging men.