Male Reproductive System 1

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Male Reproductive System 1
2011-04-12 10:33:39
Male Reproductive System

Male Reproductive System
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  1. Purpose of Male Organs
    To produce sperm and introduce them to female body
  2. Primary Sex Organs (Gonads)
  3. Secondary Sex Organs
    • Other organs needed for reproduction
    • Ducts, glands and penis
  4. External Genitalia
    • Externally visible; mostly in perineum
    • Penis, scrotum
  5. Internal Genitalia
    Not externally visible; mostly in pelvic cavity (except for testes)
  6. Secondary Sex Characteristics
    • Develop at puberty and play a role in mate attraction
    • Both sexes: pubic and axillary hair and associated with scent glands, pitch of voice
    • Male: facial hair, torso and limb hair, muscle tone
  7. Sex Determination
    • All human cells except for gametes have 23 pairs of chromosomes
    • 22 pairs of autosomes
    • Sex chromosomes (XY males, XX females)
    • Gametes have 23 chromosomes (not paired)
    • 22 Autosomes
    • X or Y
    • Egg always has x
    • Half of sperm have x, half have y
  8. Sexual Differentiation
    • For first month, fetus is sexually undifferentiated
    • Gonads develop at 5-6 weeks as gonadal ridges with ducts
  9. Mesonephric Ducts
    • Wolffian Ducts
    • Develop into male reproductive system
  10. Paramesonephric Ducts
    • Mullerian Ducts
    • Develop into female reproductive tract
  11. Prenatal Hormones and Differentiation
    • Y chromosomes contains the SRY gene (sex determining region of the Y chromosome)
    • Codes for testis-determining factor (TDF) protein
    • TDF initiates development of testes in male
    • At 8-9 weeks of age, testes begin secreting testosterone and anti-mullerian hormone (AMH)
    • Testosterone stimulates mesonephric ducts to develop into male reproductive system
    • AMH causes paramesonephric ducts to degenerate
    • Female development occurs when testosterone and AMH aren't present
  12. External Genitalia Development
    • Homologous structures in males and females
    • Genital tubercle becomes glans of the penis or clitoris
    • Urogenital folds form penis and labia minora
    • Labioscrotal folds become scrotum and labia major
    • Genitalia formed by 12 weeks of age
  13. Descent of Gonads
    • Gonads develop near the kidneys and migrate to pelvic cavity (ovaries) or scrotum (testes)
    • Gubernaculum tissue cord extends from gonad to floor of pelvic cavity
    • At about 7 months, testes pass through inguinal canal guided by gubernaculum
    • Arteries, veins, nerves, vas deferens follow testes
    • Ovary descent also guided by gubernaculum
  14. Androgen Insensitivity Syndrome
    • Occasionally a mutation on the X chromosome will mutate androgen receptors
    • Mutated receptors cannot bind to androgens
    • AIS individuals are XY, have testes, secrete normal levels of testosterone
    • External genitalia develop as female anatomy
    • No uterus, no menstruation
  15. Congenital Adrenal Hyperplasia
    • Defective enzyme to produce glucocorticoids, so androgens build up
    • (Can be XX or XY but have excess androgens)
    • CAH females have normal female internal genitalia, but often ambiguous external genitalia
    • Enlarged clitoris that can look like small penis
    • CAH females often have masculinized behavior
    • More likely to be homosexual than non-CAH women
  16. The Scrotum
    • The pouch of skin, muscle, and connective tissue containing the testes
    • Left testicle usually hangs lower than the right
    • Skin has sebaceous glands, some hair, lots of sensory nerve endings
    • Internal median septum divides septum into left and right compartments
  17. Testes
    • Produce sex hormones and sperm
    • Tunica albuginea surrounds testes
    • Tunica vaginalis membrane covers tunica albuginea
    • Testes divided into 250-300 lobules
    • Each lobule contains one or a few seminiferous tubules
  18. Histology of the Testes
    • Sperm formed in seminiferous tubules
    • Leydig (interstitial) cells produce androgens
    • Sertoli (sustentacular) cells secrete AMH and inhibin, and nurture sperm throughout their development
  19. Epididymis
    • Sperm leaves testes through rete testes to enter efferent ductules and epididymus
    • Epididymis lies on posterior surface of testis
    • Highly coiled tube divided into head, body, and tail
    • Sperm mature so that they are capable of motility and fertilization
    • Sperm stored in the tail until ejaculation
  20. Spermatic Cord
    • Bundle of connective tissue containing vas deferens, blood vessels, and testicular nerve
    • Testicular artery supplies each testis
    • Blood leaves testis through pampiniform plexus that then forms testicular veins
    • Right testicular vein drains into inferior vena cava
    • Left testicular vein drains into renal vein
    • Testicular nerves come from thoracic nerves
    • Sensory and motor neurons
  21. Vas Deferens
    • Muscular tube passing from scrotum to posterior surface of bladder
    • Carries sperm from epididymis to urethra during ejaculation
  22. Temperature Regulation
    • Testes have adapted to cooler environment (35 C), cant produce sperm at normal body temperature (37 C)
    • Temperature regulated by two muscles and countercurrent heat exchanger
    • Cremaster muscles cover the spermatic cord
    • Contract in cold temps to drop testes close to body
    • Relax in warm temps to suspend testes far from body
    • Dartos muscle: smooth muscle under scrotal skin
    • Contracts in cold to cause wrinkly scrotum
  23. Countercurrent Heat Exchanger
    • As blood travels down testicular artery, some heat is changed with cold blood in pampiniform plexus
    • Prevents arterial blood from warming testes