Changes

==Overview==

==Overview==

The colon is a site of microbial fermentation, the relative importance of this is [[#Species Differences|species dependant]]. The colon can be divided into the following portions; '''Ascending''', '''transverse''' and '''descending'''.

The colon is a site of microbial fermentation, the relative importance of this is [[#Species Differences|species dependent]]. The colon can be divided into the following portions; '''Ascending''', '''transverse''' and '''descending'''.

==Structure==

==Structure==

The following anatomical arrangement is found only in cats and dogs, see [[#Species Differences|species differences]].

The following anatomical arrangement is found only in cats and dogs, see [[#Species Differences|species differences]].

The '''ascending colon''' continues from the [[Ileum - Anatomy & Physiology|iluem]] at the '''ileocolic junction'''. It runs to the right of the '''cranial mesenteric artery''' in a caudal to cranial direction. At the cranial border of the mesentry it turns medially to become the '''transverse colon'''. The transverse colon runs from the right side of the abdomen to the left side of the abdomen. Cranial to the transverse colon is the [[Monogastric Stomach - Anatomy & Physiology|stomach]], and caudal to it is the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and '''cranial mesenteric artery'''. The '''descending colon''' continues on from the transverse colon running caudally on the left. It then passes more medially as it enters the pelvic cavity. Upon entering the pelvic cavity it is continued as the [[Rectum - Anatomy & Physiology|rectum]].

The '''ascending colon''' continues from the [[Ileum - Anatomy & Physiology|iluem]] at the '''ileocolic junction'''. It runs to the right of the '''cranial mesenteric artery''' in a caudal to cranial direction. At the cranial border of the mesentery it turns medially to become the '''transverse colon'''. The transverse colon runs from the right side of the abdomen to the left side of the abdomen. Cranial to the transverse colon is the [[Monogastric Stomach - Anatomy & Physiology|stomach]], and caudal to it is the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and '''cranial mesenteric artery'''. The '''descending colon''' continues on from the transverse colon running caudally on the left. It then passes more medially as it enters the pelvic cavity. Upon entering the pelvic cavity it is continued as the [[Rectum - Anatomy & Physiology|rectum]].

==Function==

==Function==

The colon is a site of microbial fermentation and absorption of the products of microbial fermentation, [[Volatile Fatty Acids|VFAs]]. Transportation is also important here. Motility in most species is brought about by segmentation and [http://en.wikipedia.org/wiki/Peristalsis| peristalsis]. '''Antiperistalsis''' also occurs and is particularly important in horses, ruminants and rodents. Chyme is transported towards the [[Small Intestine Overview - Anatomy & Physiology|small intestine]] so as to fill the [[Caecum - Anatomy & Physiology|caecum]]. In the horse, the antiperistaltic movements delay the movement of chyme from the ventral to the dorsal colon, which increases the time chyme is available for fermentation in the ventral colon. ''Mass movements'' move the content of the large intestine into the [[Rectum - Anatomy & Physiology|rectum]].

The colon is a site of microbial fermentation and absorption of the products of microbial fermentation, [[Volatile Fatty Acids|volatile fatty acids(VFAs)]]. Transportation is also important here. Motility in most species is brought about by segmentation and [http://en.wikipedia.org/wiki/Peristalsis| peristalsis]. '''Antiperistalsis''' also occurs and is particularly important in horses, ruminants and rodents. Chyme is transported towards the small intestine so as to fill the [[Caecum - Anatomy & Physiology|caecum]]. In the horse, the antiperistaltic movements delay the movement of chyme from the ventral to the dorsal colon, which increases the time chyme is available for fermentation in the ventral colon. ''Mass movements'' move the content of the large intestine into the [[Rectum - Anatomy & Physiology|rectum]].

==Species Differences==

==Species Differences==

===Ruminant===

===Ruminant===

The '''ascending colon''' is the longest part of the colon and is composed of three parts. The '''Ansa proximalis''' has a sigmoid flexure that passes around the caudal border of the mesentry to the left side of the root of the mesentry. The '''Ansa spiralis''' consists of two centripetal turns and two centrifugal turns in the '''ox'''. There are three turns in the sheep and four in the goat. In the ox, the ansa spiralis is a flat disc, whilst in the small ruminants it takes the form of a cone. The '''Ansa distalis''' goes back around the caudal border of the mesentry, to the right side of the root of mesentry. It then passes cranially adjacent to the mesentry until it reaches the cranial border of the mesentry. The '''transverse colon''' crosses the midline of the abdomen, from right to left at the cranial border of the mesentry. The '''descending colon''' continues caudally to the [[Rectum - Anatomy & Physiology|rectum]] and [[Anus - Anatomy & Physiology|anus]]. It has a sigmoid flexure before it enters the pelvic cavity.

The '''ascending colon''' is the longest part of the colon and is composed of three parts. The '''ansa proximalis''' has a sigmoid flexure that passes around the caudal border of the mesentry to the left side of the root of the mesentry. The '''ansa spiralis''' consists of two centripetal turns and two centrifugal turns in the '''ox'''. There are three turns in the sheep and four in the goat. In the ox, the ansa spiralis is a flat disc, whilst in the small ruminants it takes the form of a cone. The '''ansa distalis''' goes back around the caudal border of the mesentry, to the right side of the root of mesentry. It then passes cranially adjacent to the mesentery until it reaches the cranial border of the mesentery. The '''transverse colon''' crosses the midline of the abdomen, from right to left at the cranial border of the mesentery. The '''descending colon''' continues caudally to the [[Rectum - Anatomy & Physiology|rectum]] and [[Anus - Anatomy & Physiology|anus]]. It has a sigmoid flexure before it enters the pelvic cavity.

'''Development'''

'''Development'''

The ox's ascending colon expands '''caudally''' around the root of the mesentry on the left side of the mesentry (compare to horse, where it expands cranially).

The ox's ascending colon expands '''caudally''' around the root of the mesentery on the left side of the mesentery (compare to horse, where it expands cranially).

===Equine===

===Equine===

[[Image:Colon fox transverse section.jpg|thumb|right|250px|Colon (fox) - © RVC 2008]]

[[Image:Colon fox transverse section.jpg|thumb|right|250px|Colon (fox) - © RVC 2008]]

The '''mucosa''' of the colon is thick and has long glands with columnar epithelium. The '''Submucosa''' has large lymphatic nodules which may interrupt the '''lamina muscularis'''. The '''lamina muscularis''' is incomplete in the colon.

The '''mucosa''' of the colon is thick and has long glands with columnar epithelium. The '''Submucosa''' has large lymphatic nodules which may interrupt the '''lamina muscularis'''. The lamina muscularis is incomplete in the colon.

==Links==

==Links==

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

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

[[Category:To Do - Review]]

[[Category:A&P Done]]