LEC 32: TESTES & PENIS

• Testes


  Primary reproductive organ in males
• Testes


  • Responsible for spermatogenesis (sperm production) and testosterone secretion
  • 250 lobules containing seminiferous tubules
  • Spermatogenic cells & sertoli cells found within seminiferous tubules
  • Myoid cells surround seminiferous tubules, aids in sperm and fluid movement
  • Interstitial (leydig) cells produce testosterone
• Function of testes


  • Production of sperm through spermatogenesis
  • Secretion of testosterone (male sex hormone)
  • Initiates and maintains secondary male characteristics
  • Hormonal regulation of spermatogenesis by sertoli cells and leydig cells
• Importance of scrotum location

  • Provides an external environment for testes
  • Allows temperature regulation, maintains testes at 3°C lower than core body temp, crucial for sperm production
  • Responds to temp. changes, adjusts position for heat retention or loss
  • Ensures optimal condition for spermatogenesis within the testes
  • Testes supplied with blood via gonadal arteries and drained by testicular veins from a pampiniform venous plexus which steals heat from artery to keep blood from being too hot (countercurrent)
• Hormonal regulation of testicular function

  1. Hypothalamus releases GnRH

  2. GnRH stimulates anterior pituitary to release FSH and LH

  3. FSH stimulates sertoli cells, releases androgen binding protein, maintains high testosterone levels locally

  4. LH stimulates leydig cells, produces testosterone

  5. Rising testosterone inhibits GnRH release from hypothalamus & decreases gonadotropin secretion

  6. Sperm count high, inhibin released by sertoli cells inhibits FSH release when sperm count is high
• Physiological effects of testosterone


  • Initiates and maintains male secondary sex characteristics: development of pubic, axillary, facial hair, deepening of voice, thickening of skin & increased oil production
  • Promotes spermatogenesis, growth of accessory organs, development of male external genitalia
• Parts of the testis-associated reproductive duct system

  • Epididymis
  • Ductus deferens (vas deferens)
  • Ejaculatory duct
  • Urethra
• Epididymis


  • Provides a site for immature sperm to develop until expelled during ejaculation
  • Sperm gain the ability to swim while in the epididymis
  • Contains fluid with antimicrobial proteins and defensins
• Ductus deferens (vas deferens)


  • Extends as part of the spermatic cord from the epididymis, through inguinal canal, into pelvic cavity
  • Carries sperm from epididymis to the ejaculatory duct
• Ejaculatory duct


  • Passes through the prostate gland to join urethra
  • Carries sperm and seminal fluid into urethra
• Urethra


  • Terminal portion
  • Carries both urine and sperm to the exterior environment
  • Divided into: prostatic, membranous, spongy parts
• Roles of the seminal glands and the prostate

  • Seminal glands: Lies on posterior bladder wall, produces alkaline secretion containing fructose, ascorbic acid, coagulating enzyme (veniculase), prostaglandin, provides a nutrient-rich alkaline medium that nourishes and protects sperm
  • Prostate gland: Produces a milk, slightly acidic fluid containing citrate, several enzymes, prostate specific antigens, plays a role in sperm activation and motility, neutralizes the acidic pH of the vagina, enhances sperm viability and motility
• Sources and functions of semen

  • Seminal glands
  • Prostate gland
  • Bulbo-urethral gland: Produces a thick, clear mucous secretion prior to ejaculation, helps neutralize acidic urine remaining in urethra, lubricates urethra, acts as a protective medium during ejaculation
• Structure of penis


  • Covered by foreskin
  • Contains urethra and 3 erectile tissues structures: corpus spongiosum (surrounds urethra, forms the bulb of penis), paired corpora cavernosa (fills with blood during erection)
• Function of penis


  • Delivers sperm into female reproductive tract for fertilization
  • During sexual arousal, erectile tissue fills with blood, erection mediated by parasympathetic activity and nitric oxide release
  • Glans penis plays a role in sexual stimulation and orgasm
  • Expels urine and semen during ejaculation (triggered by sympathetic nervous system)