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HUMAN REPRODUCTIVE SYSTEM HL TOPIC 11.4 11.4 Reproduction • Annotate a light micrograph of testis tissue to show the location and function of interstitial cells (Leydig cells), germinal epithelium cells, developing spermatozoa and Sertoli cells. • Outline the processes involved in spermatogenesis within the testis, including mitosis, cell growth, the two divisions of meiosis and cell differentiation. • State the role of LH, testosterone and FSH in spermatogenesis. • Annotate a diagram of the ovary to show the location and function of germinal epithelium, primary follicles, mature follicle and secondary oocyte. • Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, the two divisions of meiosis, the unequal division of cytoplasm and the degeneration of polar body. • Draw and label a diagram of a mature sperm and egg. • Outline the role of the epididymis, seminal vesicle and prostate gland in the production of semen. • Compare the processes of spermatogenesis and oogenesis, including the number of gametes and the timing of the formation and release of gametes. • Describe the process of fertilization, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction • Outline the role of HCG in early pregnancy • Outline early embryo development up to the implantation of the blastocyst. • Explain how the structure and functions of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy. • State that the fetus is supported and protected by the amniotic sac and amniotic fluid. • State that materials are exchanged between the maternal and fetal blood in the placenta. • Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback GAMETOGENESIS: gamete formation SPERMATOGENESIS: production of sperms by meiotic division. OOGENESIS: production of egg cells by meiotic division. ROLES OF HORMONES • FSH: stimulates testes to produce sperm • LH: stimulates testes to produce testosterone • Testosterone: a. stimulates testes cells (leydig cells) for sperm production (meiosis) b. provides secondary sexual characteristics c. stimulates hypothalamus for the regulation of FSH and LH secretion and for reproductive behaviors. HORMONAL CONTROL OF MALE REPRODUCTIVE SYSTEM FERTILIZATION • It takes place in the upper part of the oviduct. • Uterus muscle contraction helps in drawing semen from cervix to oviduct. • When sperms reach to oocyte, they have to pass glycoprotein layer (zona pellucidia) by using their hydrolytic enzymes which are stored in their acrosome. • When a sperm cell contacts with the membrane of an egg cell sudden block reaction (electric charge changes on the membrane) takes place to prevent binding of other sperms. • Egg cell secretes chemicals (cortical granules) to provide slow block reaction to prevent binding of other sperms. • Sperm nucleus is injected into the egg cell and meiotic division of egg is cell is completed. STRUCTURE OF A SPERM CELL Figure 27.15A–B Cleavage starts Fertilization of mature egg Blastocyst Trophoblast Uterine cavity Cavity Oviduct Ovary Inner cell mass Blastocyst (implanted) Secondary oocyte Ovulation Endometrium Uterus Uterine cavity Early developmentt of an embryo Early development: Cleavage -After fertilization, zygote starts mitotic division. -Total size of the embryo does not change, the number of daughter cells increase. -Embryo reaches to 100 cells in 7 days and it starts to become embedded into the endometrium. -Inner cells become fetus. • Pregnancy, or gestation, is the carrying of developing young within the female reproductive tract. • Human pregnancy – averages 266 days (38 weeks) from fertilization or – 40 weeks (9 months) from the start of the last menstrual period. Human development begins with fertilization in the oviduct. © 2012 Pearson Education, Inc. Figure 27.15C Endometrium Uterine cavity Multiplying cells of trophoblast (contribute to future placenta) Trophoblast Embryo Future yolk sac Blood vessel (maternal) • Four extra embryonic membranes develop. 1. The amnion • surrounds the embryo and • forms a fluid-filled amniotic cavity that protects the embryo. 2. The yolk sac, • in reptiles, stores yolk, in humans, does not store yolk but is a source of the first germ cells and blood cells. 3. The allantois • contributes to the umbilical cord, • forms part of the urinary bladder, and • in reptiles, stores embryonic waste. 4. The chorion • contributes to the placenta and • secretes human chorionic gonadotropin (HCG), which prevents menstruation in mammals. © 2012 Pearson Education, Inc. Figure 27.15D Yolk sac Chorion Amnion Amniotic cavity Mesoderm cells Figure 27.15E Embryo: Endoderm Mesoderm Ectoderm Chorionic villi Chorion Amnion Allantois Yolk sac Figure 27.15F Placenta Amnion Amniotic cavity Embryo Mother’s blood Allantois vessels Yolk sac Chorion Chorionic villi • The placenta is a – close association of • embryonic chorion and • mother’s blood vessels, and – site of • gas exchange—from mother to embryo, • nutrient exchange—from mother to embryo, • waste exchange—from embryo to mother • Antibody exchange- from mother to embryo (passive immunity) – Secretion of HCG hormone • HCG maintains corpus luteum as an endocrine gland, so secretion of estrogen and progesterone continue in 16 weeks. • After 16 weeks, placenta secretes estrogen and progesterone © 2012 Pearson Education, Inc. Figure 27.16A–C January 0 Conception February 35 days March April 63 days 98 days Figure 27.16C 14 weeks (98 days) Figure 27.16D–E May June July August September October 280 days 140 days Figure 27.16D 20 weeks (140 days) Figure 27.16E At birth (280 days) Childbirth is induced by hormones and other chemical signals • Hormonal changes induce birth. – Estrogen makes the uterus more sensitive to oxytocin. – Oxytocin acts with prostaglandins to initiate labor. – The cervix dilates to about 10 cm. – The baby is expelled by strong uterine contractions. – The placenta dislodges and is expelled after the baby. © 2012 Pearson Education, Inc. Figure 27.17A Estrogen from ovaries Oxytocin from fetus and mother’s pituitary Induces oxytocin receptors on uterus Stimulates placenta to make Prostaglandins Stimulate more contractions of uterus Positive feedback Stimulates uterus to contract Figure 27.17B Placenta Umbilical cord Uterus Cervix 1 Dilation of the cervix 2 Expulsion: delivery of the infant Uterus Placenta (detaching) Umbilical cord 3 Delivery of the placenta THE PROCESS OF BIRTH 1- Contractions of uterus muscles pushes the baby to cervix. 2- Stretching of the cervix 3- stimulation of stretch –sensitive receptors in the cervix 4- Brain- control centre 5-pituitary gland secretes oxytocin 6-Uterus muscles contract more forcefully 7-further stretching of cervix 8-Birth 9-Decrease in the stretching of cervix breaks the positive feedback 10. Oxytocin secretion stops.