Avian Male Reproductive Tract - Anatomy & Physiology

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Testes

• Bean-shaped, paired
• Lie near the cranial pole of the kidney
• Medially, they lie close to the aorta and caudal vena cava.
• Each testical suspended by a short mesochorium and surrounded medially by the abdominal air sac.
• Left tends to be larger than right in immature birds.
• Dimentions increase rapidly with sexual activity.
• In the non-breeding season, testes shrink to almost nothing and become hard to visualize.
• Dormant testes light brown/yellow in colour, turn white when sexually active.
  • In some psittacine species, immature or dormant testes may appear black due to melanocytes located in the interstitium.
• Semniferous tubules produce sperm from the epithelium.
• Interstitial Leydig cells lie between semniferous tubules.
• Tunical Albiguinea thinner thsn in mammals.
• No Pampiniform plexus.
• Epididymis is small and can be considered absent. Sperm maturation occurs in the Vas Deferens.
• Vas Deferens closely associated with the Ureter in the dorsomedial midline coelom, distinguished by its zig-zag appearance.
• Vas Deferens enters dorsal wall of the Urodeum.
• No accessory sex glands.

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Phallus

• When present, the avian phallus is soley reproductive and becomes engorged by lymph fluid instead of blood during erection.
• Owing to the lack of accessory sex glands, avian semen has low volume.
  • Some lymph may contribute to the seminal fluid.
• Sperm remains viable in the female tract for much longer than in mammals.
  • May survive for 5-6 days.