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Avian Vent and Cloaca - Anatomy & Physiology (view source)
Revision as of 20:02, 2 November 2022
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==Overview==
The hindgut of the avian digestive system terminates in the '''cloaca'''. The external opening through which faecal matter and uric acid is excreted is called the '''vent'''. The shape of the vent varies depending on species.
[[Image:Avian Cloaca Diagram.jpg|thumb|right|250px|Avian Cloaca Diagram - Copyright RVC 2008]]
==The Cloaca==
The '''[[Colon - Anatomy & Physiology|colon]]''', '''[[Ureters - Anatomy & Physiology|ureters]]''' and '''deferent ducts'''/'''left [[Avian Female Reproductive System#Oviduct|oviduct]]''' enter at various levels. It can be divided into the '''coprodeum''', '''urodeum''' and '''proctodeum''' by complete annular folds. Some urinary excretions arriving in the cloaca become incorporated with the ingesta and move in a retrograde fashion to the [[Caecum - Anatomy & Physiology|caeca]], increasing the absorption of water and electrolytes from the urinary waste.
The '''coprodeum''' is the most cranial division of the cloaca. It is the continuation of the colon where faeces are stored. It is bounded by the '''coprourodeal fold'''. It can be stretched by the faecal pressure so the central opening is everted through the vent.
The '''urodeum''' is the middle part of the cloaca. It is caudal to the '''proctodeum fold'''. It has the ureteric opening in the dorsolateral wall above the papilla of the deferent duct/[[Avian Female Reproductive System#Oviduct|oviduct]] opening.
[[Image:Bursa of Fabricus.jpg|thumb|right|250px|Bursa of Fabricus - Copyright Nottingham 2008]]
The '''proctodeum''' is the caudal segment. It is short and ends at the vent. The opening in the dorsal wall leads to the cloacal '''bursa of Fabricus'''.
==The Vent==
The vent is a horizontal slit. It has the [[Avian Male Reproductive Tract - Anatomy & Physiology#Phallus|phallus]] of males on the internal surface of the ventral lip. During insemination, the vent is inverted.
==Histology==
The avian vent and cloaca consist of columnar epithelium. Stratified squamous epithelium are present at the external opening of the vent and in the '''caudal proctodeum'''. There are broad folds of mucous membrane forming crypts, which branch near their base. Lymphoid tissue is present in the submucosa. The fold of mucous membrane covering the entrance to the bursa is composed of columnar epithelium, muscle, connective tissue and goblet cells. There are two layers of tunica muscularis; '''inner circular''' and '''outer longitudinal'''.
==Species Differences==
'''Galliformes''' (turkeys and chickens) can move urates from the urinary tract into the [[Colon - Anatomy & Physiology|colon]] and [[Caecum - Anatomy & Physiology|caeca]] where ammonia is released for protein synthesis. A small membrane covers the opening of the [[Avian Female Reproductive System #Oviduct|oviduct]] into the cloaca in '''ducks''', '''geese''' and '''swans''' until sexual maturity.
==Links==
'''Click here for information on the [[Bursa of Fabricius - Anatomy & Physiology|Bursa of Fabricus]]'''
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==Webinars==
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[[Category:Avian Alimentary System - Anatomy & Physiology]]
[[Category:Avian Reproduction]]
[[Category:A&P Done]]