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Rabbit Alimentary System (view source)

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==Introduction==

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The rabbit is a monogastric hindgut ~~fermenters~~ and is a herbivore. Microbes in the hindgut produce [[Volatile Fatty Acids|VFAs]] which are available to the animal for energy. Microbes also produce vitamins and protein, which are available only in minimal quantities as they are produced in the hindgut. Most microbial fermentation occurs in the [[Caecum - Anatomy & Physiology|caecum]] (as opposed to the [[Equine Alimentary System - Anatomy & Physiology|horse]] where most occurs in the colon). Rabbits usually eat at dusk.

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The rabbit is a monogastric hindgut fermenter and is a herbivore. Microbes in the hindgut produce [[Volatile Fatty Acids|VFAs]] which are available to the animal for energy. Microbes also produce vitamins and protein, which are available only in minimal quantities as they are produced in the hindgut. Most microbial fermentation occurs in the [[Caecum - Anatomy & Physiology|caecum]] (as opposed to the [[Equine Alimentary System - Anatomy & Physiology|horse]] where most occurs in the colon). Rabbits usually eat at dusk.

==[[Monogastric Stomach - Anatomy & Physiology|Stomach]]==

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*Simple and large

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The rabbit has a simple and large stomach.

==[[Small Intestine Overview - Anatomy & Physiology|Small Intestine]]==

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*Functions similar to other animals but there are anatomical differences.

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*The caudal flexure of the [[Duodenum - Anatomy & Physiology|duodenum]] is long and coiled, and may be referred to as the transverse part of the duodenum.

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*The sacculus rotundus exists at the ileocaecal junction. It is an enlargement of the [[Large Intestine - Anatomy & Physiology|large intestine]] and contains [[Lymphatic System - Anatomy & Physiology|lymphoid tissue]].

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==[[Large Intestine Overview - Anatomy & Physiology|~~Large~~ Intestine]]==

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A rabbit's small intestine functions similar to other animals, but there are anatomical differences. The caudal flexure of the [[Duodenum - Anatomy & Physiology|duodenum]] is long and coiled, and may be referred to as the transverse part of the duodenum.

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The sacculus rotundus exists at the ileocaecal junction. It is an enlargement of the [[Large Intestine - Anatomy & Physiology|large intestine]] and contains [[Lymphatic System - Anatomy & Physiology|lymphoid tissue]].

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==Large intestine==

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Click here for information on the [[Large Intestine Overview - Anatomy & Physiology|large Intestine]].

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===[[Caecum - Anatomy & Physiology|Caecum]]===

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==[[Caecum - Anatomy & Physiology|Caecum]]==

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*Large, about twice the length of the abdominal cavity and 10 times the capacity of the stomach, 40% of the entire alimentary tract.

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*Folded into four parts that flex upon each other.

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*Thin-walled.

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*Visible on the external surface is a spiral constriction that runs 20-30 times around the caecum. This is related to the folding of the mucosa internally.

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*There is an [[Appendix - Anatomy & Physiology|appendix]] at it's distal end containing [[Lymphatic System - Anatomy & Physiology|lymphoid tissue]].

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===[[Colon - Anatomy & Physiology|Colon]]===

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A rabbit's caecum is large, about twice the length of the abdominal cavity and 10 times the capacity of the stomach, 40% of the entire alimentary tract. It is folded into four parts that flex upon each other. It is thin-walled. Visible on the external surface is a spiral constriction that runs 20-30 times around the caecum. This is related to the folding of the mucosa internally.

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*Has ascending, transverse and descending parts.

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There is an [[Appendix - Anatomy & Physiology|appendix]] at it's distal end containing [[Lymphatic System - Anatomy & Physiology|lymphoid tissue]].

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*The '''ascending colon''' is very long and occupies most of the ventral abdomen.

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*First part has taenia and haustra, the second part does not and is arranged into coils that lie in the dorsal part of the abdominal cavity.

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==[[Colon - Anatomy & Physiology|Colon]]==

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*The '''transverse''' and '''descending''' colons have the same anatomical arrangement as in other species.

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A rabbit's colon has ascending, transverse and descending parts. The '''ascending colon''' is very long and occupies most of the ventral abdomen. The first part has taenia and haustra, the second part does not and is arranged into coils that lie in the dorsal part of the abdominal cavity. The '''transverse''' and '''descending''' colons have the same anatomical arrangement as in other species.

==Coprophagia==

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*Rabbits eat some of their faecal pellets, called '''caecotropes''', directly from the [[Anus - Anatomy & Physiology|anus]].

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*Caecotropes differ to normal pellets as they are softer, covered in mucus, smaller and contain large amounts of bacteria and microbes.

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Rabbits eat some of their faecal pellets, called '''caecotropes''', directly from the [[Anus - Anatomy & Physiology|anus]]. Caecotropes differ to normal pellets as they are softer, covered in mucus, smaller and contain large amounts of bacteria and microbes. The purpose of this may be to gain access to the vitamins produced by bacteria in the [[Caecum - Anatomy & Physiology|caecum]]. Some microbial protein may also be available, but is thought to contribute little to the animal's requirement, as most is digested in the colon. Therefore, some amino acids (lysine and methionine) are added to commercial rabbit food. This behaviour is also seen in rodents.

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*The purpose of this may be to gain access to the vitamins produced by bacteria in the [[Caecum - Anatomy & Physiology|caecum]].

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*Some microbial protein may also be available, but is thought to contribute little to the animal's requirement, as most is digested in the colon.

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**Therefore some amino acids (lysine and methionine) are added to commercial rabbit food.

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~~***~~This behaviour is also seen in rodents.

==Calcium Metabolism==

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*Rabbits have a unique calcium metabolism.

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*Calcium is absorbed across the intestinal wall in the absence of vitamin D, which other mammals require for calcium absorption.

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*Less regulated calcium absorption results in calcium being excreted in the urine.

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*Parathyroid hormone and [[Calcium Homeostasis - Anatomy & Physiology|calcitonin]] regulate blood levels.

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**Kidney stones and calcification of soft tissue may occur if a high calcium diet is fed to rabbits for a prolonged period of time.

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Rabbits have a unique calcium metabolism. Calcium is absorbed across the intestinal wall in the absence of vitamin D, which other mammals require for calcium absorption. Less regulated calcium absorption results in calcium being excreted in the urine. Parathyroid hormone and [[Calcium Homeostasis - Anatomy & Physiology|calcitonin]] regulate blood levels. Kidney stones and calcification of soft tissue may occur if a high calcium diet is fed to rabbits for a prolonged period of time.

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~~==Test yourself with the Hindgut Fermenters Rabbit Flashcards==~~

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*[[Rabbit Alimentary System - Flashcards|Rabbit Revision Flashcards]]

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'''Test yourself with the [[Rabbit Alimentary System - Flashcards|Rabbit Revision Flashcards]]'''

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[[Category:Rabbit - Alimentary System]]

[[Category:Large Intestine - Anatomy & Physiology]]

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[[Category:To Do - ~~A&P~~]]

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[[Category:To Do - AimeeHicks]]

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