Male Reproductive System

• Male Reproductive System


  • Testes (within the scrotum) produce sperm and testosterone
  • Epididymis, ductus deferens, ejaculatory duct, and the urethra deliver sperm to the exterior
  • Accessory sex glands (seminal vesicles, prostate, and bulbourethral glands) empty secretions into the ducts during ejaculation
• The Scrotum


  • Sac of skin and superficial fascia
  • Hangs outside the abdominopelvic cavity
  • Contains paired testes
  • Temperature is kept 3°C lower than core body temperature by 2 sets of muscles (dartos muscle and cremaster muscles)
• The Testes


  • Each is surrounded by two tunics (tunica vaginalis and tunica albuginea)
  • Septa divide the testis into 250–300 lobules, each containing 1–4 seminiferous tubules (site of sperm production)
  • Blood supply comes from the testicular arteries and testicular veins
  • Spermatic cord encloses nerve fibers, blood vessels, and lymphatics that supply the testes
  • Interstitial (Leydig) Cells outside the seminiferous tubules produce androgens
  • Sustentacular (Sertoli) Cells around the seminiferous tubules create tight junctions to form the blood-testes barrier
• The Penis


  • Male copulatory organ consisting of root, shaft, and glans penis
  • Prepuce or foreskin is the cuff of loose skin covering the glans
  • Crura are the proximal end surrounded by ischiocavernosus muscle that anchors the penis to the pubic arch
  • Spongy urethra and three cylindrical bodies of erectile tissue (corpus spongiosum, corpora cavernosa) fill with blood during erection
• The Male Duct System

  1. Epididymis nourishes maturing sperm

  2. Ductus (Vas) deferens inside spermatic cord propels sperm during ejaculation

  3. Ejaculatory duct

  4. Urethra (prostatic, membranous, penile/spongy regions) for both urine and semen
• Accessory Glands


  • Seminal Vesicles produce viscous alkaline seminal fluid
  • Prostate secretes milky, slightly acid fluid containing citrate, enzymes, and prostate-specific antigen (PSA)
  • Bulbourethral Gland (Cowper's Glands) produce thick, clear mucus to lubricate the glans penis
• Semen


  • Mixture of sperm and accessory gland secretions
  • Alkalinity neutralizes the acid in the male urethra and female vagina
  • Only 2–5 ml of semen are ejaculated, containing 20–150 million sperm/ml
• Spermatogenesis


  1. Occurs in the seminiferous tubules

  2. Starts at puberty and continues throughout life

  3. Involves spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids, and sperm
• Sperm


  • Head (genetic region with nucleus and acrosome)
  • Midpiece (metabolic region with mitochondria)
  • Tail (locomotor region with flagellum)
• Sexual Response


  1. Erection: engorgement of erectile tissue with blood via nitric oxide, corpus cavernosa expands, corpus spongiosum keeps urethra open (parasympathetic reflex)

  2. Ejaculation: sympathetic reflex

  3. Men have refractory period after ejaculation
• Hormonal Regulation of Male Reproductive Function

  Hypothalamic-pituitary-gonadal (HPG) axis: hypothalamus releases GnRH, stimulating anterior pituitary to secrete FSH and LH, which regulate spermatogenesis and testosterone production
• Testosterone


  • Synthesized from cholesterol, transformed in some tissues to exert its effects
  • Responsible for secondary sex characteristics and anabolic effects throughout the body
  • Basis of sex drive (libido) in males
• Testicular Cancer is the most common cancer in males between the ages of 20-35, with early signs of a mass on the testes, testicular pain, and a dull ache in the abdominal region
• Prostate Cancer can be indicated by elevated PSA levels, and signs of an enlarged prostate include frequent urination, painful urination, and inability to void urine
• Erectile Dysfunction is the consistent inability to obtain or hold an erection, or inability to ejaculate, caused by insufficient nitric oxide, penile abnormalities, testosterone deficiency, or systemic disorders
• Corpus spongiosum surrounds the urethra and expands to form the glans and bulb
• Corpora cavernosa are paired dorsal erectile bodies
• Circumision is the surgical removal of the foreskin
• How many regions does the male urethra have?

  Three; prostatic urethra, membranous urethra, and penile or spongy urethra
• Where are the seminal vesicles located?

  Posterior-inferior aspect of bladder
• What is the primary role of alkalinity in semen?

  Neutralize the acid in the male urethra
• What is the consistent inability to obtain/hold an erection called?

  Erectile Dysfunction (Impotence)