BISC 307L 1st Edition Lecture 20 Current Lecture Structure of Testes o o o o o o o mostly seminiferous tubules leydig cells in between the tubules are the testosterone secreting cells big cells sertoli cells surround and nourish sperm small cells spermatogonia stem cells differentiation occurs as they move acrosome contains enzymes and carbohydrates that swell when they contact water so that they can penetrate the oocyte o takes 70 days before you get sperm every day several hundred million sperm are produced o if not ejaculated they just get destroyed Endocrine Control of Testicular Function o o Control begins with the GnRh secreted in the hypothalamus o Testosterone feeds back and stimulates the sertoli cells Reproduction 2 Female Reproductive Anatomy o ovary is where testes used to be the follicle produces the oocyte o mature oocyte expelled into the abdomen into the oviduct where it is stored for a while If there are sperm present during this time then fertilization can occur o long trip for the sperm o the zygote stays there and them moves down to the uterus to be implanted o the uterus has three layers 1 Endometrium 2 Myometrium 3 Outer connective tissue o cervix is the opening between the uterus and upper part of the vaginalocked with a acidic mucus plug and acts as a barrier to sperm penetration and bacteria Development of the Ovarian Follicle 1 o Ovarian follicle Oogenesis Female fetus several million oogonia stem cells will be produced during fetal life and begin meiosis during fetal life but then become arrested during the first meiotic division primary oocytes later some of these oocytes will be surrounded by a single layer of granulose cells like sertoli cells These become the primary follicles 2 million at time of birth Every day starting at birth and continuing throughout life about 30 of these primary follicles begin to differentiate along the path in the drawing but unless the hormone levels are appropriate then the oocytes will not complete differentiation and die This means that you run out about 45 50 years old BUT in 2004 conflicting evidence in adult female mice which had small numbers of stem cells in their ovaries that are oocyte stem cells which was not thought to exist in adult females They were able to show that this is true and they are capable of producing oocytes and capable of producing little mice Last month show that in the ovaries of reproductive age women there are these stem cells that can give rise to mature oocytes competent for fertilization Secondary follicle with a few layers basal lamina and theca cells analogous to the leydig cells Endocrine Control Ovarian Function o o granulosa cell converts testosterone to estradiol which stimulates granulosa cells o positive feedback in rapid growth of the follicle Development of the Ovarian Follicle 2 o o Secondary follicle needs FSH to continue why of the 900 follicles that begin this process only a handful of them will continue when FSH is at the exact right level cells proliferate and secrete fluid from granulose cells which become the antrum and the follicle begins bulging on the surface of the ovary pressure inside the antrum builds meanwhile the outlying tissue is being digested this positive feedback causes levels of estradiol to rise and the pressure in the antrum grows until there is a rupture in the follicle oocyte expelled into the abdomen remnants of the follicle are called the corpus luteum made of granulosa cells produces estradiol and progesterone LH causes the yellowing of this and causes ovulation the corpus luteum requires gonadotropin support and the high levels of estrogen are inhibiting FSH and LH secretion so if fertilization doesn t occur the feedback inhibition will cause the corpus luteum will regress and become the corpus albicans
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