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[[Image:Cockatiel.jpg|thumb|right|200px|Cockatiel - Copyright nabrown 2008]]
==Introduction==
Birds are endothermic vertebrates, many with a high core temperature of 41.3°C. The rapid heart rate (93-494 bpm) and respiratory rate (12-85) explain the fast metabolic rate of the avian species. This high basic metabolic rate influences the rate of drug absorbtion, metabolism and excretion and should be taken into account when anaesthetising these animals.
The avian ailimentary system differs immensely from the basic mammalian design. Food can move in a retrograde fashion from the [[Proventriculus - Anatomy & Physiology|proventriculus]] to the [[Crop - Anatomy and Physiology|crop]]. Food can also pass from the [[Gizzard - Anamtomy & Physiology|gizzard]] back into the [[Proventriculus - Anatomy & Physiology|proventriculus]] depending on particle size, which is similar to that in mammals. The egestion of bones occurs once the nutritious material has been ingested. During reflux, gastric motility is inhibited and the pellet is expelled through the [[Avian Oral Cavity - Anatomy & Physiology|oral cavity]] by oesophageal antiperistaltis. This cleans the [[Crop - Anatomy and Physiology|crop]] out and checking the pellet of captive birds should be undertaken daily to assess health.
The avian [[Avian Intestines - Anatomy & Physiology|intestines]] shows some species specific anatomical variety, and the hindgut of the avian digestive system differs from mammalian anatomy as it terminates in the [[Avian Vent and Cloaca - Anatomy & Physiology|cloaca]]. The external opening through which faecal matter and uric acid is excreted is called the [[Avian Vent and Cloaca - Anatomy & Physiology|vent]]. The shape of the vent varies depending on species. Avian species vary in the presence or absence of a [[Avian_Liver_-_Anatomy_%26_Physiology#Gallbladder:_Species_Differences|gall bladder]], and the avian [[Avian Liver - Anatomy & Physiology|liver]] differs from the mammalian liver, being bilobular.
[[Image:Avian GIT.jpg|thumb|right|200px|Avian GIT Overview - Copyright Nottingham 2008]]
[[Category:Avian Digestive Tract - Anatomy & Physiology]]