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.
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.
Absence of Phallus
- Psittacines, Passerines, Pidgeons and birds of prey all have no phallus.
- Copulate by transferring semen from the everted Cloaca directly into the female oviduct.