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Avian Male Reproductive Tract - Anatomy & Physiology (view source)
Revision as of 14:01, 5 July 2012
, 14:01, 5 July 2012→Lymphatic Folds
== Introduction ==
Paired reproductive tracts lie along the dorsal body wall. Each tract consists of a testis, a rudimentary epididymis and a highly convoluted deferent duct running alongside the ureter. The testes are connected to the body wall by a mesochorium. This peritoneal fold serves as an attachment for the testes and also a conduit for nerves and blood vessels.
== Testes ==
== Testes ==
[[Image:Chicken male dissection.jpg|thumb|right|150px|Dissection of the Male Avian Reproductive Tract- Courtesy of Andrew Crook, Copyright RVC 2008]]
* Bean-shaped, paired
* Bean-shaped, paired
* Lie near the cranial pole of the kidney
* Lie near the cranial pole of the kidney
* Medially, they lie close to the aorta and caudal vena cava.
* 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.
* 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.
* Left tends to be larger than right in immature birds.
* Dimentions increase rapidly with sexual activity.
* Dimensions increase rapidly with sexual activity.
* In the non-breeding season, testes shrink to almost nothing and become hard to visualize.
* 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.
* 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.
** In some psittacine species, immature or dormant testes may appear black due to melanocytes located in the interstitium.
* Tunical Albiguinea thinner than in mammals.
* '''No Pampiniform plexus'''.
'''''Semniferous Tubules'''''
* Convoluted '''semniferous tubules''' comprised of '''spermatogonia''' (germ cells) and '''Sertoli cells''' make up the bulk of the testes. These are responsible for '''spermatogenesis'''.
* '''Interstitial Leydig cells''' produce male androgens.
* Interstitial Leydig cells lie between semniferous tubules.
* Mature spermatozoa exit into the '''rete testes''', which connects to the cranial '''epididymis'''.
** Rete testes not present in all birds.
** Epididymis considered vestigial in birds.
*** Sperm maturation occurs in the '''ductus deferens'''.
* Epididymis lies along the dorsomedial aspect of the testes.
* Spermatazoa exit the epididymis and enter the ductus deferens.
** Ductus deferens is closely associated with the Ureter in the dorsomedial midline coelom, distinguished by its zig-zag appearance.
** Under hormonal control, more convoluted in the breeding season.
* Ductus deferens enters the dorsal wall of the '''cloacal urodeum'''.
** Straightens and abruptly widens at ats junction with the cloaca.
*** Structure known as the '''receptacle''' in Passerines and Budgerigars.
*** Receptacle appears bean-shaped when engorged with semen.
*** Birds that do not have the receptacle structure have little sperm storage capacity.
== Phallus ==
== Phallus ==
* Most birds lack a true phallus.
* Analogue of the mammalian penis.
* Consists of a small median tubercle flanked by a pair of large, lateral phallic bodies.
* 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 [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|Cloaca]] directly into the female [[Avian Female Reproductive System#Oviduct|oviduct]].
=== Non-Protrusible Phallus ===
* Rudimentary non-protrusible phallus is seen in male Turkeys and Chickens.
* Lies on the ventral lip of the vent.
* Consists of a small medial tubercle intimately associated on each side with lymphatic folds and vessels.
* When erect with lymph, the phallus develops a median groove.
** Median groove permits passage of ejaculate down into the everted female [[Avian Female Reproductive System#Oviduct|oviduct]].
=== Protrusible Phallus ===
* Ratites and Anseriformes
* Elongated, capable of true intromission into the female [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|cloaca]].
* Distal end lies enclosed in a cavity on the floor of the [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|cloaca]] and becomes engorged with lymphatic fluid.
** Anseriformes have a curved, fibrous phallus that conveys semen via a spiral groove.
== Accessory Sex Organs ==
The male avian has no [[Accessory Sex Glands - Anatomy & Physiology|accessory sex glands]] that are seen in mammals. Instead, they have accessory reproductive organs:
* Paracloacal Vascular Bodies
* Dorsal Procotodeal Gland
* Lymphatic Folds
These are either in proximity to, or are an integral part of the [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|cloaca]].
=== Paracloacal Vascular Bodies ===
* Found alongside the receptacle of the vas deferens.
* Contribute to the lymphatic erection of the either cloacal or phallic tissue.
* Release a lymph-like transparent transudate when engorged.
=== Dorsal Procotodeal Gland ===
* Found on the dorsal [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|proctodeum]].
* Develop to varying degrees.
* Undergo [[Cell Growth Disorders#Hypertrophy|hypertrophy]] in response to '''steroid sex hormones'''.
=== Lymphatic Folds ===
* Found within the wall of the [[Avian_Vent_and_Cloaca_- Anatomy & Physiology#The_Cloaca|procotodeum]].
* Contribute to the lymphatic erection of the either cloacal or phallic tissue.
* Release a lymph-like transparent transudate when engorged.
[[Category:Avian Reproduction]]
[[Category:Bullet Points]]