bio 11

• Male reproductive system


  • Consists of compatible female and male organs for sexual reproduction
  • Responsible for the production of haploid gametes
  • Spermatogenesis and oogenesis
  • Secretes hormones responsible for development & maintenance of reproductive systems and secondary sexual characteristics

  
• Levels of organization of the male reproductive system

  • Testes
  • System of ducts (epididymis, vas deferens, ejaculatory ducts, urethra)
  • Accessory sex glands (seminal vesicles, prostate gland, bulbourethral gland)
  • Supporting structures (scrotum and penis)

  
• Spermatogenesis


  1. Spermatogonium in seminiferous tubules produce sperm by meiosis

  2. Spermatids differentiate into sperm cells

  3. 50% of sperm have X chromosome, 50% have Y chromosome
• Sperm cells


  • Head (acrosome, nucleus)
  • Tail (mitochondria, flagella)

  
• Sperm flow


  1. Seminiferous tubules

  2. Epididymis

  3. Ductus (Vas) Deferens

  4. Ejaculatory duct

  5. Urethra

  
• Semen

  • Mixture of sperm cells and secretions from accessory glands
  • 50-150 million sperm per mL
  • Slightly alkaline (pH 7.5)
  • Contains prostaglandins which trigger uterine contractions
• Erection, Emission and Ejaculation

  1. Erection (relaxes vascular smooth muscle, blood fills erectile tissue)

  2. Emission (small discharge of semen before ejaculation)

  3. Ejaculation (powerful release of semen from urethra)
• Erectile dysfunction / Impotence


  • Inability to produce an erection
  • Physiological or psychological causes (damage to nervous system/arteries, lifestyle, stress/anxiety, depression)
  • Viagra (Sildenafil) inhibits relaxed smooth muscles from re-contracting, increasing blood flow
• Hormonal regulation of spermatogenesis

  1. Hypothalamus produces GnRH

  2. GnRH stimulates anterior pituitary to produce FSH and LH

  3. FSH stimulates Sertoli cells to support spermatogenesis

  4. LH stimulates Leydig cells to produce testosterone which also stimulates spermatogenesis
• Testosterone


  • Steroid hormone
  • Required for development of male genitalia
  • Stimulates development of sperm and sexual drive
  • Promotes secondary sexual characteristics and protein synthesis
• High testosterone levels


  Negative feedback on hypothalamus and anterior pituitary, decreasing GnRH and LH secretion
• Adequate spermatogenesis


  Sertoli cells secrete Inhibin, which decreases FSH secretion
• 50% of sperm have an X chromosome and 50% have a Y chromosome
• Will this be true of female gametes?