Male Reproductive System

• Parts of the male reproductive system


  • Testis
  • Epididymis
  • Ductus deferens
  • Accessory glands
  • Penis
• Functions of the male reproductive system


  • Produce sperm
  • Store and transport the sperm
  • Produce seminal fluid
  • Ejaculate
  • Secrete testosterone
• Testis


  Organ to produce sperm and testosterone
• Testis


  • Made of seminiferous tubules
• Epididymis


  Accumulation, storage & maturation of spermatozoa
• Epididymis


  • Head, body, tail
  • Continuous to the ductus deferens which enters the pelvic cavity
• Sperm transfer


  Seminiferous tubules -> epididymis -> Vas deferens
• Testes - Gross Anatomy (dog)


  • Sacrotuberous ligament
  • Caudal gluteal vessels
  • Internal pudendal vessels
  • Anus
  • Pelvic urethra
  • Bulb of penis enclosed by bulbospongiosus
  • Ischiocavernosus over left crus
  • Body of penis
  • And 9' = bulbus and pars longa glandis
  • Spermatic cord, ductus deferens, cremaster muscle
  • Testes in scrotums
  • Dorsal artery and vein of the penis
  • Femoral vessels
• Accessory sex glands


  • Seminal vesicles (=vesicular gland)
  • Prostate gland (main)
  • Bulbourethral (Cowper's) gland
• Accessory sex glands


  Add nutrients and may contribute the final volume of the seminal fluid (not all present in every species)
• Ampulla of Ductus Deferens


  Drains sperm to the urethra
• Penis


  • Rigidity = tumescence (swelling)
  • Mammalian penis engorged with blood
  • Avian phallus engorges with lymph
  • Os penis in some species
  • Muscular contractions -> muscles massage the urethra to move sperm
• Prepuce


  • Skin sheath concealing penis in quiescent state
  • Formed from abdominal skin
  • Stallions (uncastrated male horse) have an extra fold
• Anatomy of the Penis


  • 3 columns of erectile tissue
  • Corpus Cavernosum x2
  • Corpus Spongiosum
  • Penis divided anatomically into: Root, Body, Free part
• Corpus Cavernosum Penis (CCP)


  • Paired, start at crus (pl. Crura)
  • Dorsal to urethra
  • Enclosed in tunica albuguinea
• Types of Corpus Cavernosum Penis


  • Fibroelastic = boar and ruminant
  • Musculocavernous = stallion, man, and dog (atypical)
• Fibroelastic Corpus Cavernosum Penis


  • Small cavernous spaces divided by tough fibroelastic tissue
  • Less blood is required for erection
  • Sigmoid flexure at the body of penis – allows extrusion at coitus
• Musculocavernous Corpus Cavernosum Penis


  • Larger cavernous spaces divided by muscular tissue
  • More blood required for erection
  • Erection involves significant increase in length & girth
• Corpus Spongiosum Penis (CSP)


  • Spongy sleeve around urethra
  • Enlarged to form Bulb of penis
  • Expands over the apex of penis to form Glans
  • More delicate than CCP with larger blood spaces
• Anatomy of the Penis


  • Erectile tissue of CSP and CCP made of numerous cavernous spaces (filled with blood)
  • Cavernous spaces divided by trabeculae
  • Trabecular composed of: Smooth muscle, Fibroblasts, Collagen, Elastic fibres, Endothelial cells
• Species Differences in Penis


  • Dog & cat distal part of CCP bone = os penis
  • Glands penis different
• Ischiocavernosus muscle


  • Originate ischial arches and enclose around crura till their fusion
  • Compress the crus part of corpus cavernosum against the ischium thus occluding veins and preventing venous return from CCP
• Bulbospongiosus muscle


  • Surround the corpus spongiosum
  • Covers the root of the penis ventral to CSP
  • Continuation of urethralis muscle
  • Empties extrapelvic urethra of sperm
  • Circular striated muscle
• Refractor penis muscle


  • Paired
  • Originates caudal vertebrae down perineum around anal canal to ventral penis
  • Retracts penis
  • Smooth muscle
• Arterial supply of Penis


  • External (to skin) and internal (to CCP, CSP) pudendal arteries
• Venous Draining of Penis

  • CCP: Supply - root of penis, Drainage - root of penis
  • CSP: Supply - bulb of penis, Drainage - from distal part of penis
• Erection, intromission, and ejaculation


  1. Vascular, neurological and endocrine systems work together

  2. Erection: contraction of the ischiocavernosus muscle -> occlusion of venous outflow

  3. Relaxation of corpus cavernosum and corpus spongiosum via parasympathetic nerve

  4. Intromission: mounting behaviour

  5. Emission: release of spermatozoa and accessory gland fluids into the pelvic urethra

  6. Ejaculation: forceful expulsion of semen from the urethra

  7. Post-ejaculation: increase in the smooth muscle tone of the cavernous space -> increase of outflow of blood, contraction of the refractor penis muscle withdraws the penis into the prepuce
• Male reproductive endocrine axis


  Gonadotropin-Releasing Hormone (GnRH) -> FSH, LH -> Leydig cells, Sertoli cells -> Testosterone, inhibin
• Descend of testes in embryos


  1. Gonad develops retroperitoneally

  2. Sperm cannot develop at core body temp

  3. Gubernaculum is a ligament connecting the gonad to the future scrotum via inguinal canal and 'pulls down' the gonad

  4. While descending, testes push all layers of the abdominal wall

  5. A part of the peritoneum also descends together and forms tunica vaginalis (vaginal tunic)
• Testicular Descent


  • Testes descend through inguinal canal to scrotum usually before birth
  • Failed descent prevents sperm production & can cause neoplasia
• Open or closed castration


  • = open or does not open the vaginal tunic
  • = cut the layers of [internal spermatic fascia and parietal vaginal tunic] or not