Gero 310 F'09 repro male

Gero 310 F'09 repro male - Male reproductive system Normal...

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Normal function, physiology and anatomy Normal function, physiology and anatomy • functions Male reproductive system Male reproductive system 1. reproduction - main goal of living species is to successfully reproduce; principle of evolution - involves haploid gametes: sperm 2. sexual activity 3. hormone production - gonadal sex steroid hormones: testosterone , dihydro- testosterone (DHT) Chp 13
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• anatomy * gonads - testes , enclosed within scrotum (keeps optimal temperature @ ~34°C) * genitals - penis * accessory glands, structures - seminal vesicles, prostate, bulbourethral gland
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• hormones - testosterone & dihydrotestosterone (DHT) - produced by Leydig cells in testes - aka interstitial cells - located in seminiferous tubules
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testosterone aromatase 5 α -reductase • testosterone activates both estrogen & androgen pathways - precursor to estradiol and DHT - enzymes that metabolize testosterone to estradiol (aromatase) and DHT (5 α -reductase) are localized in various hormone responsive tissues estrogen receptors androgen receptors estradiol DHT
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- system is designed for continuous production of large number of sperm - strategy: large number of sperm to increase probability of successful fertilization • reproductive process - sperm generated in testes within the seminiferous tubules - occurs via meiosis called spermatogenesis - mature sperm stored in epididymis (located just above testes)
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- during sexual activity, ejaculation occurs - sperm travel from epididymis through vas deferens and into urethra - vas deferens site of vasectomy - surgical birth control option - urethra is tube located within penis - urethra carries urine as well as sperm - during ejaculation, bladder is closed off - fluids are added to sperm from several glands, including seminal vesicles , prostate , bulbourethral gland - fluids + sperm called semen - fluids add energy (fructose) and neutralize acidic environment of urethra • reproductive process (cont.)
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- approximately 400 million sperm released @ ejaculation - sperm is mobile - swims to relatively stationary egg - only one sperm permitted to successfully penetrate and fertilize egg • reproductive process (cont.)
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Age-related changes in male reproductive system 1) decrease in testosterone levels Blackman et al. (1988) J. Clin. Endo. Metab. • normal aging is associated with a decrease in bioavailable testosterone • total testosterone declines by ~1% per year after age 30 • also, sex hormone binding globulin (SHBG) increases with age - SHBG binds testosterone - T not biologically available when bound to SHBG • thus, bioavailable T decreases at a greater rate than total T, ~2% per year
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Harman et al. (2001) J. Clin. Endo. Metab. • Baltimore Longitudinal Study of
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This note was uploaded on 01/16/2011 for the course GERO 310 taught by Professor Davies during the Fall '09 term at USC.

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Gero 310 F'09 repro male - Male reproductive system Normal...

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