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BIOLOGY 12 Reproductive System Introduction to the Reproductive System http://www.youtube.com/watch?v=444fTSTuhjg&feature=related Introduction • We humans like all mammals, have internal fertilization and development. • This requires specialized organs for both sexes. Male Reproductive System •Testis – 2 oval shaped glands outside the body sperm and hormone production •Seminiferous tubules – 3 coiled tubes approx. 250m in length which carry out meiosis spermatogenesis / sperm production •Interstitial cells cuboidal cells surrounding the seminiferous tubules which are responsible for producing testosterone •Scrotum – thin layer of skin (sac) containing testis •Epididymis – tube just outside the testes where sperm is stored and matures. Testis Seminiferous Tubules • Vas deferens (ductus deferens) small muscular tube leaving the testicles conducts semen from epididymis • Seminal vesicle, prostate gland, and Cowpers gland (bulbourethral gland) – all three are glandular organs PROSTATE (largest) contribute to seminal fluid (contents of semen to be discussed later) • Penis – erectile tissue (spongin) copulatory organ • Glans penis – end of the penis containing large number of sensory receptors stimulation • Foreskin – thin layer of skin over glans protection • Urethra – muscular tube conducts semen and urine • Corpus cavernosum – contains spongin becomes engorged with blood when vein is constricted • Urinary bladder – hollow muscular organ holds urine Male Sexual Response • Upon sexual arousal, the primary response is to have the penis become erect. • This is necessary to achieve internal fertilization. • Upon arousal, NO (nitrogen oxide) is released from cells at the base of the penis. • Blood vessels dilate allowing blood to flow into the corpus cavernosum. • This is called vasocongestion. • Once the penis is erect, coitus, which is the insertion of the penis into the vagina can occur. • The erection is maintained until an orgasm is reached. • The penis contains a tissue along the top of made of spongin and cartilage. • This engorgement creates pressure on the penal vein, closing it resulting in the erection. • This continues as long as the tissue is stimulated by the parasympathetic nervous system to keep releasing NO. SPERMATOGENESIS The Sperm Cell • Smallest cell in the body - contains three regions: A. The head: made of the acrosome and the haploid nucleus. B. The Mid Piece: containing many mitochondria. C. The Tail: - a flagellum (9 x 2 pattern of microtubules). Male Hormone Regulation • The Interstitial cells between the seminiferous tubules begin to secrete Testosterone from puberty on. • This is responsible for male secondary sex traits and the male sexual responses. HORMONE CONTROL Two pituitary hormones regulate male reproductive physiology: 1) Follicle Stimulating Hormone (FSH) • FSH is released from the anterior pituitary and targets the seminiferous tubules initiating spermatogenesis. 2. Lutenizing Hormone (LH) • Also released by the anterior pituitary but it targets the Interstitial (Leydig) cells to produce testosterone. • Both pituitary hormones are regulated by negative feedbacks. Negative Feedback LOOP Gonadotropic releasing hormone Follicle stimulating hormone Leutenizing hormone Increases sperm production Increases testosterone TESTOSTERONE • The effects of testosterone are: Increase penis growth Facial, body, pubic and axillary hair Enlarged larynx Bone and muscle growth Increased sex drive Acne The Female System The female system is actually a dual system: reproduction and providing an environment for development of the fetus Human Ovary and Fallopian Tube Human Uterus: l.s. FEMALE REPRODUCTIVE SYSTEM Female Reproductive Organs ANATOMY / PHYSIOLOGY • Ovaries – glandular organs (gonads) size of • • • • • small lemons developing eggs (oogenesis), and produces sex hormones Uterus – strong muscular organ, holds the developing fetus Endometrium ( uterine lining) nourishes the developing embryo Cervix – opeining to the uterus forms a plug holding in the amniotic fluid during pregnacy Vagina – muscular organ copulation and birth canal Labia majora, labia minora – outer folds of skin forming the vulva protection • Clitoris – organ of stimulation similar to the glans penis in males • Bartholin’s gland aids in lubrication prior to orgasm • Fimbrae – sweep egg up into fallopian tubes when the ovary ruptures and releases egg • Fallopian tubes (oviducts) lined with tiny ciliated cells which sweep egg and usually site of fertilization • Urethra – conducts urine from bladder • Urinary Bladder – holds urine Ovarian cycle is divided into 2 phases; 1) Follicular Phase where the egg matures and is released from the ovary 2) Luteal Phase following the release of the egg, the corpus luteum forms and continues to release the hormone progesterone which is responsible for maintaining the endometrium lining. OVARIAN CYCLE 1. Primary follicle containing an “oocyte” egg begins to produce sex hormone estrogen 2. Secondary follicle containing primary oocyte continues to develop. 3. Graafian follicle matures 4. Ovulation occurs when the Graafian follicle ruptures releasing the oocyte. 5. Corpus luteum produces the sex hormone progesterone and estrogen. 6. Corpus luteum gradually disinterates if the egg is not fertilized. The Reproductive Cycle of the Human Female Menstrual cycle: changes that occur in the uterus. Day 1: the first day of menstruation. Menstrual flow phase. Menstrual bleeding. Usually lasts for a few days. Proliferative phase. Regeneration and thickening of the endometrium. About 1 – 2 weeks in duration. Secretory phase. Continued endometrial thickening, increased vascularization of the endometrium, endometrium develops glands that secrete a glycogen-rich fluid, and a duration of about 2 weeks. • If, by the end of the secretory phase, an embryo has not implanted in the uterus a new menstrual flow commences. Fig. 46.15d Hormonal Control Hormonal coordination of the menstrual and ovarian cycles involves five hormones. Gonadotropin releasing hormone (GnRH) secreted by the hypothalamus. Follicle-stimulating hormone (FSH) secreted by the anterior pituitary. Luteinizing hormone (LH) secreted by the anterior pituitary. Estrogens secreted by the ovaries. Progesterone secreted by the ovaries. GnRH stimulates secretion of small amounts of FSH and LH. FSH stimulates the growth of immature ovarian follicles. The growing follicles secrete small amounts of estrogens. Inhibits secretion of FSH and LH. FSH and LH levels remain relatively low. The rate of secretion of estrogens by the growing follicle rises steeply. Stimulates the secretion the GnRH. Stimulates the secretion of FSH and LH. LH secretion is especially high. LH induces the final maturation of the follicle and ovulation. The follicular phase of the ovarian cycle is coordinated with the proliferative phase of the menstrual cycle. Secretion of estrogens during the follicular phase stimulates endometrial thickening. Negative feedback Loop Estrogen / Progesterone Secondary Sex Characteristics Breast growth Mensturation Pubic hair Widening of hips Acne Distribution of fat Mood swings Developing Oocyte Menopause Cessation of ovarian and menstrual cycles. Usually occurs between ages 46 and 54. Due to ovaries decreased responsiveness to gonadotropins. The Female System B. Fertilization • Occurs in the top one third of the Fallopian tubes. • Once ovulated, the egg is only viable for about 24 hours if not fertilized. • Events of fertilization will be studied in detail when we do development next. The Female System C. Contraception • Except for condom, all are female directed. i. The Pill: 2 types • Estrogen Pill: causes negative feedback on pituitary production of FSH - therefore, the follicle doesn’t develop in the ovary. • Progesterone Pill: feeds back upon LH production - no LH surge - no ovulation. The Female System ii. The Intra-uterine Device • Placed in uterus - prevents embryo from implanting. • May also be spermicidal. iii. Rhythm method: • Based upon avoiding sex during fertile periods of menstrual cycle. The Female System iv. Tubal Ligation • Involves surgery to cut a short section out of each fallopian tube to prevent egg getting to sperm. • Male equivalent is vasectomy. v. Diaphragm • Used with foams and gels to act as physical barrier of sperm into uterus. The Female System 3. Implantation and Pregnancy • After fertilization, the zygote continues to move down the fallopian tube. • As it does, development begins (details later). • It takes the embryo 7 - 12 days to get to the uterus and implant in the endometrium. Cleavage to Blastula Implantation The Female System • As it implants, it secretes a hormone called Human Chorionic Gonadotropin (HCG). • This acts like LH and continues to stimulate the corpus luteum to secrete progesterone. • If this didn’t happen, menstruation would happen with the loss of the endometrium and the embryo in it. • HCG can be detected in the mothers urine. The Female System • Progesterone also triggers other anatomical and physiological changes in the mother. • This includes: breast development, uterine growth, and placental development. Conception to BIRTH http://www.youtube.com/watch?v=AoisqOGQIVE&feature=r elated Development Period of the Embryo • For the first three months, organogenesis occurs and it is termed an embryo. • This is a 6 week embryo. Development Period of the Fetus • During the second trimester, HCG declines and the placenta secretes its own progerestone. • This is the period of the fetus marked by growth of all the organs. • This is a 4 month fetus. Development Period of the Baby • The third trimester, period of the baby, is marked by growth and maturation of all organs and organ systems. • The baby is capable of life outside the womb during this period. A. Labor: secretions of oxytocin from the posterior pituitary cause the cervix to Birth contract and open. • When dilated to 10 cm., the next phase begins. B. Birth of the baby: • Typically delivered head first. Postive Feed back loop during LABOUR C. Delivery of the Afterbirth • About half hour after the baby is born, the uterus contracts again to expel the placenta and membranes. • The uterus then contracts tightly to seal off all the broken capillaries. Reproductive Diseases 1. AIDS (Acquired Immunity Deficiency Syndrome) • Caused by the Human Immunodeficiency Virus. • HIV positive means the virus is present. • Transmitted through sexual contact via mucous membranes • Is actually a fragile virus that does not live long outside of a host. • Can cross the placenta. • Common in drug addicts sharing needles. • Drug cocktails are prolonging the life of AIDS victims but there is no cure and death from it is inevitable. 2. Genital Herpes • Most common sexually transmitted disease. • Caused by Herpes simplex virus. • Causes blisters, ulcers, severe itching, fever, and painful urination 2 - 20 days after infection. • Heals by itself but is still very contagious. Can recur anytime and is very difficult to get rid of. Genital Herpes Reproductive Diseases 3. Gonorrhea - caused by a bacteria • In males, results in a yellowish discharge of pus from penis painful urination. • In females, effects less obvious until fully infected. Reproductive Diseases • Infects vagina and uterus and can cause PID - Pelvic Inflammatory Disease - which can lead to major problems as well as permanent sterility. • Baby can be infected during birth - eyes. • Easily treated with antibiotics. Reproductive Diseases 4. Chlamydia - small bacterium • Effects are similar to gonorrhea but less severe and often not diagnosed or treated. • Frequent cause of female sterility. A leading cause of blindness in children. Picture shows clouding of cornea due to chlamydia. Reproductive Diseases 5. Syphilis - spirillum bacteria. • A most ancient disease. Picture shows ancient skull with damage due to syphilis First Stage: chancre sore at site of infection. Primary Syphilis: Chancre sores Chancre on penis on labia Secondary Syphilis • Second Stage: nonitchy rash over body. Tertiary Syphilis Third Stage: Tertiary Syphilis • Large ulcerated sores over body and on internal organs. • Attacks nervous system - insanity. • Eventually, leads to death. Tertiary Syphillis • Syphilis is a scourge of children worldwide. • It is almost epidemic in Africa. • Still common in North America.