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Repro Lecture 1 male.docx

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Michelle French

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Repro: Lecture 1: male October-26-12 1:15 PM Common between males and females • Formation of gametes (spermo/ocytes) •Hypothalamic/pituitray control of reproduciotn Gametogenesis •Gametes withb 23 chromosomes are produced from cells in the gonads with 46 chromosomes •Precess involves meiosis o DNA replicated once o Cells undergo division twice •In contrast : mitosis = normal cell division o DNA replicated once o Cells undergo division once Mitosis vs. Meiosis (crossing over also happens, mixing of DNA) Hypothalamic/pituitary control of reproduction •Internal and environmental stimuli in CNS _> GnRH •GnRH (gonadotropin releasing hormone) in hypothalamus ->anterior pituitary •-GnRh in anterior pituitray -> LH and FSH •LH -> endocrine cells -> steroid and peptide hormones, gamete produciton in females •FSH-> gamete prduction •LH is the main regulator of endocrine secetion from the gonads •Steroid hormones long loop feedback either positive or negative on GnRH •GnRH in ant. Short loop Negatively feedbacks GnRH in hyp GnRH secreted in pulses from neuroendocrine cells in hypothalamus •Pulsatility critical for reproductive function •Regulated by hormonal feedback and higherbrain centres •Pulse frequency/amplitude changes during brain development •If pulsatility is absent, no reproduction •When hyp neurons fire, gnrh is released (triggered by electrical activity) Male reproductive system •Same passage for semen and urine o Sphincter that prevents urine form being released with semen •Testes in scrotum •Sperm starts at the scrotum, goes through vas deferens to get to seminal vesicle and then out through utrethra Sperm produciton • Produced in testis •Optimal at 2-3 degrees lower than body temperature •Takes ~64 days • 200 million/day • Further mature in epididymis (also in scrotum?) Microscopic view of testis • Sertoli cells (sustentacular cells)- support sperm development • Leydig cells (interstitial cells) - secrete testosterone • Spermatagonia can divide and some of their daughter cells can divide further o Some will stay as spermatagonia and others will develop further (most immature cells) • Tight junctions responsible for blood testis barrier Spermatogenesis • Spermatogonia (2n) in sertoli cells that was formed during fetal development -> mitosis and differentiation o After mitosis one spermatogonium stays to produce more • primary spermatocytes (2nx2) o Starting to develop o The other cell begins to undergo meiosis forming spermatocytes • Secondary spermatocytes and spermatids o 4 spermatids produced from one starting cell o Still have to mature as they lack flagellum • Spermatozoa: spermatids mature into spermatozoa o Lose cyto
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