Handout 3 answers

Handout 3 answers - BICD 150 — Summer 2011 Ni Mo Week 3:...

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Unformatted text preview: BICD 150 — Summer 2011 Ni Mo Week 3: Handout #3 jeffnimo@gmail.com Material Covered: Male Reproduction OH: Tuesday 1-2pm Peterson Hall Lobby Male Reproduction Gross Anatomy: The male external genitalia consist of: penis, scrotum, prostate The male accessory structures consist of: vas deferens, seminal vesicle, epididymis Mechanism of erection: Acetylcholine targets endothelial cells 9 activate mACh receptor 9 f [Ca2+] 9 activate NOS 9 1‘ NO 9 activate guanylyl cyclase 9 f cGMP 9 relaxation of smooth muscle (vasodilation) 9 erection Microscopic Anatomy: The testes contain two types of cells: - Leydig cells 0 Targeted by _LH_ o Secretes: _testosterone___ - Sertolicells 0 Targeted by_FSH__ o Secretes: I _Androgen binding protein— ' _Inhibin_ - _Anti-Mullerian hormone— "Tb \ . K Gametogenesis ‘ U“ K (d‘l’t A) MitosiS ' _c wflff Z- -- --l, - -- _ j.25_—rysezn_\ A l, WA’W’wW‘ rugs/my :1 WWW @ i° qutvc‘K / \J or mom Amen a.“ Secrmbfi" \ / \Qmi meiotic Juiwsuim ® gW‘X i l .L l an/ marl—«Art SWAN Embryonic State/Pre-puberty: - Spermatogonium (diploid) undergoes mitotic division to make more spermatogonia Puberty and Later: - Spermatogonia continue to undergo mitotic division - Some of these spermatogonia undergo DNA replication and crossing-over of sister chromatids to make primary spermatocytes (diploid + duplicated) - First meiotic division results in secondary spermatocytes (haploid + duplicated). - Then, these secondary spermatocytes undergo the second meiotic division, which results in spermatids (haploid) - These spermatids then mature into haploid sperms. Androgens Synthesis: - Precursor for all androgens: _cholesterol . This is transported into the mitochondrial matrix via transporter called _$tAR protein_ — Once in the matrix, cholesterol is converted to _pregnenolone , which can go through a variety of pathways to make other androgens. DHEA (dehydroepiandrosterone) — weak androgen that is also synthesized in adrenal glands by both males and females. - Oxidation results in synthesis of androstenedione, which is the precursor for testosterone Testosterone - consists of the majority (95%) of androgens produced - Testosterone is responsible for the development of the _Wolffian__ duct into male accessory structures. - In addition, testosterone is also responsible for the secondary male sexual characteristics (e.g. hair growth, larynx/vocal cord growth, 1 muscle mass, etc.) - Testosterone can be converted to the more potent _dihydrotestosterone via enzyme _5-a-reductase_. This hormone is what is responsible for the primary male sexual characteristics (e.g. external genitalia). If one abuses anabolic steroids, one of the signs is infertility. Why? Elevated exogenous steroids exhibit negative feedback to GnRH. J GnRH -) I FSH/LH -) infertility. Sexual Development \m )5 We} spy Y W I 7294: WW“: (WA?) duhslcnwu. GD Wol‘m‘q/ -0! 1.64 . a “mum owe/ta mo ® 6 {vulan M35" DU \1/ AM 5 emf {Nua Mm c Mmbs The process: ( (Wag! if"!!! Ha - Early embryos are i he bipotential sta e, and the ggnads contain both a cortex and a medulla. Sex is determined by presence or absence of SRY gene (usually found on Y chromosome). - The presence of SRY gene will allow the medulla to develop into testes. o In the testes, there are two types of cells: leydig and sertoli. o The leydig cell secretes testosterone, which is responsible for development of Wolffian duct into accessory structures. 0 In addition, testosterone may be converted to DHT via enzyme 5-a-reductase. DHT is responsible for development of male external genitalia. o The sertoli cell secretes anti-Mullerian hormone, which degrades the Mullerian duct. — The absence of SRY gene will allow the cortex to develop into ovaries. o In the ovaries there are also two types of cells: theca and granulosa. o The theca cell is equivalent to the leydig cell in males and secretes androgens (such as testosterone, DHEA, and androstenedione). o The granulosa cell contains the enzyme aromatase, which is used to convert androgens into estradioI/estrogen. What would happen if a XY embryo were missing S-a-reductase? Female external genitalia + testes + male accessory organs What would happen if a XY embryo had nonfunctional androgen receptors? Female external genitalia + testes ...
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Handout 3 answers - BICD 150 — Summer 2011 Ni Mo Week 3:...

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