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Premium member Presentation Transcript Fisiologi Reproduksi : Fisiologi Reproduksi Frincia Bunga Rante Allo 08-052 Slide 2: Sexual reproduction is the formation of a new individual following the union of two gametes. Gametes need: motility to be able to meet and unite food to nourish the developing embryo. Sex Organs of the Human Male : Sex Organs of the Human Male The reproductive system of the male has two major functions: production of sperm delivery of these to the reproductive tract of the female. Sperm production — spermatogenesis — takes place in the testes. Sex Organs of the Human Male : Sex Organs of the Human Male Each testis is packed with seminiferous tubules (laid end to end, they would extend more than 20 meters) where spermatogenesis occurs. Spermatogenesis : Spermatogenesis The walls of the seminiferous tubules consist of diploid spermatogonia, stem cells that are the precursors of sperm. Having two of each kind of chromosome (except for the sex chromosomes); 2n A cell that gives rise to both differentiated descendants as well as more stem cells Spermatogonia : Spermatogonia divide by mitosis to produce more spermatogonia or differentiate into spermatocytes. - It distributes one of each duplicated chromosome (as well as one centriole) to each daughter cell. It is convenient to consider mitosis in 4 phases. PMAT Spermatogenesis : Spermatogenesis Meiosis of each spermatocyte produces 4 haploid spermatids. This process takes over three weeks to complete. Then the spermatids differentiate into sperm, losing most of their cytoplasm in the process. Sperm : Sperm Sperm cells are little more than flagellated nuclei. Each consists of a head, which has an acrosome at its tip and contains a haploid set of chromosomes in a compact, inactive, state. a midpiece containing mitochondria and a single centriole a tail Sperm : Sperm An adult male manufactures over 100 million sperm cells each day. These gradually move into the epididymis where they undergo further maturation. The acidic environment in the epididymis keeps the mature sperm inactive. Sperm : Sperm In addition to making sperm, the testis is an endocrine gland. Its principal hormone, testosterone, is responsible for the development of the secondary sex characteristics of men. Testosterone is also essential for making sperm. Testosterone is made in the interstitial cells that lie between the seminiferous tubules. Sex Organs of the Human Female : Sex Organs of the Human Female The responsibility of the female mammal for successful reproduction is considerably greater than that of the male. She must: manufacture eggs be equipped to receive sperm from the male provide an environment conducive to fertilization and implantation nourish the developing baby not only before birth but after Oogenesis : Oogenesis Egg formation takes place in the ovaries. In contrast to males, the initial steps in egg production occur prior to birth. Diploid stem cells called oogonia divide by mitosis to produce more oogonia and primary oocytes. By the time the fetus is 20 weeks old, the process reaches its peak and all the oocytes that she will ever possess (~4 million of them) have been formed. By the time she is born, 1–2 million of these remain. Each has begun the first steps of the first meiotic division (meiosisI) and then stopped. Oogenesis : Oogenesis No further development occurs until years later when the girl becomes sexually mature. Then the primary oocytes recommence their development, usually one at a time and once a month. The primary oocyte grows much larger and completes the meiosis I, forming a large secondary oocyte and a small polar body that receives little more than one set of chromosomes. Which chromosomes end up in the egg and which in the polar body is entirely a matter of chance. Oogenesis : Oogenesis In humans (and most vertebrates), the first polar body does not go on to meiosis II, but the secondary oocyte does proceed as far as metaphase of meiosis II and then stops. Only if fertilization occurs will meiosis II ever be completed. Entry of the sperm restarts the cell cycle breaking down MPF (M-phase promoting factor) and turning on the anaphase promoting complex (APC). Oogenesis : Oogenesis The ripening follicle also serves as an endocrine gland. Its cells make a mixture of steroid hormones collectively known as estrogen. Estrogen is responsible for the development of the secondary sexual characteristics of a mature woman. Estrogen continues to be secreted throughout the reproductive years of women During this period, it plays an essential role in the monthly menstrual cycle. Ovulation : Ovulation Ovulation occurs about two weeks after the onset of menstruation. In response to a sudden surge of LH, the follicle ruptures and discharges a secondary oocyte. This is swept into the open end of the fallopian tube and begins to move slowly down it. Hormonal regulation of monthly ovarian cycle : Hormonal regulation of monthly ovarian cycle Day 1 Rising levels of GnRH stimulate release of FSH & production of LH by anterior pituitary FSH stimulates proliferation of granulosa cells & the follicle grows Granulosa cells secrete follicular fluid producing small fluid-filled cavities which merge to form the fluid-filled antrum Increasing numbers of granulosa cells release estrogens & inhibin 6-8 Inhibin & estrogen decrease GnRH release & FSH releaseHigher levels of estrogen stimulate production & release of LH (positive feedback) LH accelerates growth & maturation of follicle (1 dominant ovum) 12-14 While follicle migrates to ovarian surface, estrogen level increases sharply causing a surge of LH & 1 follicle ruptures & releases ovum. Other follicles degenerate forming atretic follicles. Estrogen levels fall. 15 LH levels are elevated for 2 days, cause follicle cells to be filled with lipid & yellow pigment (luteinized) forming a corpus luteum. The corpus luteum secretes progesterones & estrogens which inhibit the hypothalamus production of GnRH & decrease FSH & LH levels 26 Corpus luteum degenerates & forms the corpus albicans if there is no pregnancy. Decreasing levels of progesterone & estrogen result in renewed production of GnRH The Menstrual Cycle : The Menstrual Cycle About every 28 days, some blood and other products of the disintegration of the inner lining of the uterus (the endometrium) are discharged from the uterus, a process called menstruation. During this time a new follicle begins to develop in one of the ovaries. After menstruation ceases, the follicle continues to develop, secreting an increasing amount of estrogen as it does so. The Menstrual Cycle : The Menstrual Cycle The rising level of estrogen causes the endometrium to become thicker and more richly supplied with blood vessels and glands. A rising level of LH causes the developing egg within the follicle to complete the first meiotic division (meiosis I), forming a secondary oocyte. After about two weeks, there is a sudden surge in the production of LH. This surge in LH triggers ovulation: the release of the secondary oocyte into the fallopian tube. The Menstrual Cycle : The Menstrual Cycle Under the continued influence of LH, the now-empty follicle develops into a corpus luteum (hence the name luteinizing hormone for LH). Stimulated by LH, the corpus luteum secretes progesterone which -continues the preparation of the endometrium for a possible pregnancy -inhibits the contraction of the uterus -inhibits the development of a new follicle The Menstrual Cycle : The Menstrual Cycle If fertilization does not occur (which is usually the case), -the rising level of progesterone inhibits the release of GnRH which, in turn, -inhibits further production of progesterone. As the progesterone level drops, -the corpus luteum begins to degenerate; -the endometrium begins to break down, its cells committing programmed cell death (apoptosis); -the inhibition of uterine contraction is lifted, and -the bleeding and cramps of menstruation begin. Uterine Cycle : Uterine Cycle Day 1Menses: degeneration & loss of the functional layer. Decrease in progesterones & estrogens stimulates the release of prostaglandins which cause the spiral arterioles to constrict. O2 & nutrient deprivation causes endometrial necrosis, desquamation & bleeding. Only the stratum basalis remains. 5-14Proliferation: restoration of the functional layer. Follicular cells secrete increasing amounts of estrogen. Stratum basalis cells proliferate producing the s. functionalis. Short straight endometrial glands form, spiral arterioles regrow. 15-26Secretion: increased growth & secretion prepares uterus for implantation. Levels of progesterones & estrogens produced by the corpus luteum increase. Glands enlarge, coil into corkscrew shapes & secrete glycogen. Vascularization of the s. functionalis increases. 26-28If fertilization does not occur, the corpus luteum degenerates and progesterone & estrogen levels decline. IMPLANTATION : IMPLANTATION TERIMA KASIH : TERIMA KASIH You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.