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Alimentary System - Horse Anatomy (view source)
Revision as of 21:38, 7 November 2012
, 21:38, 7 November 2012→Large Intestine
In the hindgut of the horse; 75-85% of insoluble carbohydrates is digested, 15-30% of soluble carbohydrates and 30% of protein digestion. A lot of absorption of [[Volatile Fatty Acids|volatile fatty acids (VFAs)]] and water occurs in the large intestine which pass readily into the blood. Electrolytes are also absorbed in the large intestine; 95% of sodium and chloride and 75% of potassium and phosphate.
In the hindgut of the horse; 75-85% of insoluble carbohydrates is digested, 15-30% of soluble carbohydrates and 30% of protein digestion. A lot of absorption of [[Volatile Fatty Acids|volatile fatty acids (VFAs)]] and water occurs in the large intestine which pass readily into the blood. Electrolytes are also absorbed in the large intestine; 95% of sodium and chloride and 75% of potassium and phosphate.
To mix the contents of the large intestines, the taenia and circular muscle of the tunica muscularis contract. This also transports the ingesta through the large intestine and brings the products of fermentation in contact with the epithelium.
To mix the contents of the large intestines, the taenia and circular muscle of the tunica muscularis contract. This also transports the ingesta through the large intestine and brings the products of fermentation in contact with the epithelium.
===[[Caecum - Anatomy & Physiology|Caecum]]===
The caecum is the main site of microbial fermentation, followed by the ascending then descending [[Colon - Anatomy & Physiology|colons]]. It is located on the right side of the abdomen. It is very large, roughly 1m in length with a 30L capacity. It consists of a base, body and apex (blind ending). The base lies in the right dorsal part of the abdomen, in contact with the abdominal roof. The apex lies on the ventral abdominal wall, and terminates at the level of the '''xiphoid cartilage'''. It exists at the junction with the [[Ileum - Anatomy & Physiology|ileum]] and [[Colon - Anatomy & Physiology|colon]].
The '''caecocolic orifice''' is where the caecum opens into the ascending colon. This exists as a transverse slit formed by a constriction of the ascending colon. There is a sphincter at this point which prevents backward flow of ingesta when the colon contracts.
The ileum opens into the caecum at the '''ileal papilla'''. This is a small projection into the caecum housing the ileal sphincter and venous plexus that, together, control the ileal orifice.
'''Taenia''' are present. Taenia are formed by concentration of the ''longitudinal'' muscle layer. Between the taenia are sacculations, or '''haustra'''. Haustra appear as folds on the interior surface. There are '''four''' taenia over the [[Caecum - Anatomy & Physiology|caecum]]; dorsal, ventral, lateral and medial. The '''dorsal''' taenia provides the attachment site for the ileocaecal fold, which joins the caecum to the [[Ileum - Anatomy & Physiology|ileum]].
The '''lateral''' taenia provides the attachment site for the caecocolic fold, which joins the caecum to the ascending [[Colon - Anatomy & Physiology|colon]]. The '''ventral''' taenia is free.
The '''medial''' and '''lateral''' taenia are where the caecal vessels and [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] are located. Ingesta is regularly transported from the [[Ileum - Anatomy & Physiology|ileum]] to the [[Caecum - Anatomy & Physiology|caecum]], this movement can be heard upon auscultation of the right dorsal quadrant of the caudal abdomen.
Ausculatation of this area is carried out in the assesment of colic. In the horse, the [[Caecum - Anatomy & Physiology|caecum]] is responsible for the digestion of complex carbohydrates such as cellulose.
===[[Colon - Anatomy & Physiology|Colon]]===
====Ascending colon====
The ascending colon is very large and takes up most of the ventral abdomen. It is the shape of a double "U", where one "U" is on top of the other. There are four limbs that lie parallel to each other, and three flexures that change these direction of the limbs.
The sequence of the limbs and flexures of the ascending colon is as follows; '''Right Ventral Colon''' ''(for those with an RVC bias remember, "the RVC comes first!")'', passes out of the caecocolic orifice on the right side of the abdomen and continues cranially to the xiphoid region; '''Sternal Flexure''', passes across the midline from right to left, '''Left Ventral Colon''', runs caudally on the left ventral abdominal floor; '''Pelvic Flexure''', turns dorsally just cranial to the pelvic inlet and then runs cranially to the diaphragm, '''Left Dorsal Colon''', runs cranially, parallel and dorsal to the left ventral colon; '''Diaphragmatic Flexure''', turns caudally at the diaphragm; '''Right Dorsal Colon''', continues caudally on the right. It is the shortest limb of the ascending colon.
The '''transverse colon''' continues on from the right dorsal colon as the right dorsal colon turns medially. The right dorsal colon is attached by a mesentery to the dorsal abdominal wall, the base of the [[Caecum - Anatomy & Physiology|caecum]], the root of the mesentry and the [[Pancreas - Anatomy & Physiology|pancreas]]. This anatomical arrangement of mesentery allows the left ascending colon to twist and is a common cause of colic ([[Large Colon Torsion - Horse|colonic torsion]]).
The ventral parts of the ascending colon are attached to the dorsal parts by a short '''mesocolon'''. The mesocolon houses the blood vessels, nerves and lymphatics. In the ventral colon many important digestive and absorptive functions take place, whilst the dorsal colon is mainly responsible for transportation of ingesta. '''Taenia''' are present. Different parts of the colon can be distinguished by the number of taenia present:
The right and left ventral colon and the sternal flexure have '''four''' taenia. The left dorsal colon and pelvic flexure have '''one''' taenia and the right dorsal colon and diaphragmatic flexure have '''three''' taenia.
====Transverse Colon====
The transverse colon is short. It passes from across the midline from right to left. It passes cranial to the root of the mesentery
The transverse colon has '''two''' taenia. It turns caudally to become the descending colon at the level of the [[Urinary System Overview - Anatomy & Physiology|left kidney]].
====Descending Colon====
The descending colon is between 2-4m long. It is suspended by a long mesentery; ''mesocolon descendens''. The descending colon has '''two''' taenia. Between the two taenia are distinct sacculations that house the faecal balls.
==Liver==
==Liver==
==Pancreas==
==Pancreas==