Avian Male Reproductive Tract - Anatomy & Physiology

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.