Male Reproductive System - Physiology and Anatomy - Lecture Slides, Slides of Physiology

Download Male Reproductive System - Physiology and Anatomy - Lecture Slides and more Slides Physiology in PDF only on Docsity! Male Reproductive System 20-25 Docsity.com Male Reproductive System • Testes contain seminiferous tubules (STs) where spermatogenesis occurs; & interstitial tissue housing T-secreting Leydig cells • Sertoli cells of STs contain receptors for FSH – FSH stimulates spermatogenesis • Leydig cells contain LH receptors – LH stimulates secretion of T Fig 20.12 20-26 Docsity.com Testosterone & Age • Secretion of T declines gradually & varyingly in men> 50 – Causes are unknown – Not due to low GnRH, LH, or FSH because their levels are elevated 20-29 Docsity.com Endocrine Function of the Testes • T & derivatives (androgens & estradiol) are responsible for body changes at puberty – Stimulate growth of larynx, bone, & Hb levels – Are called anabolic steroids because stimulate muscle growth – These & local peptides play paracrine roles in supporting spermatogenesis 20-30 Fig 20.15 Docsity.com Spermatogenesis • Germ cells that migrate from yolk sac during development become spermatogonia (stem cells) – Spermatogonia replicate selves throughout life by mitosis – Give rise to haploid sperm by meiosis Fig 20.16 20-31 Docsity.com Sertoli Cell Function • Autoimmune destruction of developing sperm is prevented by blood- testes barrier created by Sertolis – & by Sertoli-secreted FAS ligand that triggers apoptosis of T cells • Spermatogonia & developing spermatozoa are embedded in, & nurtured by, adjacent Sertolis 20-34 Docsity.com Sertoli Cell Function continued • Sertolis secrete androgen-binding protein (ABP) into lumen of STs – ABP binds testosterone, concentrating it in tubules • FSH stimulates spermiogenesis through its receptors on Sertolis • Sertolis provide negative feedback on FSH via production of inhibin 20-35 Docsity.com Spermatozoa • Have oval-shaped head that contains DNA & the acrosome (a cap of digestive enzymes) • Have a midpiece & flagellar tail – Tail will become motile in epididymus 20-36 Docsity.com Male Accessory Sex Organs • Spermatozoa & fluids exit STs via rete testis • Pass through efferent ductules to epididymis & leave through vas deferens 20-38 Docsity.com Male Accessory Sex Organs continued • Spermatozoa entering epididymis are non-motile & cannot fertilize – In part because pH is low • Spermatozoa mature & become motile in epididymis • Prostatic fluid neutralizes pH during ejaculation 20-39 Docsity.com Male Accessory Sex Organs continued • Vas deferens carries sperm into pelvic cavity • Seminal vesicles add fluid (constituting 60% of ejaculate) to that coming from epididymis – Contains fructose for energy for sperm • Vas deferens becomes ejaculatory duct which merges with urethra in prostate 20-40 Docsity.com Emission & Ejaculation • Emission is movement of semen into urethra • Ejaculation is forcible expulsion of semen from urethra out of penis • Both are stimulated by sympathetic activity – Which also causes peristalsis of tubular system, contractions of seminal vesicles, prostate, & muscles at base of penis 20-43 Docsity.com Male Fertility • Normal volume of ejaculate is 1-5 ml – With 60-150 million sperm/ml • Sperm count of < 20 million/ml constitutes oligospermia – Associated with decreased fertility – Caused by heat, lead or arsenic poisoning, & drugs • Including marijuana, cocaine, & anabolic steroids 20-44 Docsity.com Male Contraception • Efforts have targeted gonadotropin secretion (with limited usefulness because of side effects) • Vasectomy is one of most widely used methods – Each vas deferens is cut & tied – Sperm can’t enter urethra; accumulate in crypts along reproductive tract • Where sperm are phagocytosed by immune system • 70% develop anti-sperm antibodies 20-45 Docsity.com