| Line 1: |
Line 1: |
| − | <big><center>[[Alimentary - Anatomy & Physiology|'''BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY''']]</center></big>
| + | #REDIRECT[[:Category:Large Intestine - Anatomy & Physiology]] |
| − | | |
| − | ==Introduction==
| |
| − | | |
| − | The large intestine extends from the [[Ileum - Anatomy & Physiology|ileum]] of the [[Small Intestine - Anatomy & Physiology|small intestine]] to the [[Anus - Anatomy & Physiology|anus]]. Water, electrolytes and nutrients are absorbed, concentrating the ingesta into faeces. Faeces are stored prior to defeacation. No chemical digestion takes place; there is no secretion of enzymes. All species have a large microbial population living in the large intestine, which is of particular importance to the [[Hindgut Fermenters - Anatomy & Physiology|hindgut fermenters]]. For this reason, hindgut fermenters have a more complex large intestine with highly specialised regions for fermentation.
| |
| − | | |
| − | The large intestine can be divided into:
| |
| − | | |
| − | *[[Caecum - Anatomy & Physiology|Caecum]]
| |
| − | *[[Colon - Anatomy & Physiology|Colon]]
| |
| − | *[[Rectum - Anatomy & Physiology|Rectum]]
| |
| − | *[[Anus - Anatomy & Physiology|Anus]]
| |
| − | | |
| − | ==Structure==
| |
| − | | |
| − | ==Function==
| |
| − | | |
| − | | |
| − | ==Vasculature==
| |
| − | | |
| − | *The '''cranial mesenteric artery''' supplies the caecum, ascending and part of the transverse colon.
| |
| − | *The '''caudal mersenteric artery''' supplies the rest of the transverse colon, the descending colon and the rectum.
| |
| − | | |
| − | ==Innervation==
| |
| − | | |
| − | *Like the [[Small Intestine - Anatomy & Physiology|small intestine]], the large intestine recieves sympathetic and parasympathetic innervation.
| |
| − | *Neurones interact with the myenteric plexus to affect contractility, and with the submucosal plexus to affect secretions.
| |
| − | **The '''sympathetic '''have coeliac, cranial mesenteric and caudal mesenteric ganglia.
| |
| − | **As the sympathetic fibres leave the ganglia, they surround their respective artery.
| |
| − | **'''Parasympathetic''' innervation stimulates peristalsis.
| |
| − | | |
| − | ==Lymphatics==
| |
| − | [[Image:Colon fox lymphatic nodule.jpg|thumb|right|150px|Lymphatic Nodule - Copywright RVC 2008]]
| |
| − | *Lymphatic nodules are present in the mucosa.
| |
| − | | |
| − | ==Histology==
| |
| − | [[Image:mucosal layer of colon.jpg|thumb|right|150px|Mucosal Layer of Colon (Fox) - Copywright RVC 2008]]
| |
| − | *The mucosa of the large intestine is smooth; there are '''no villi'''.
| |
| − | *Mucosal glands are much longer and straighter.
| |
| − | *The number of goblet cells in the mucosa is increased compared to the small intestine.
| |
| − | **Mucus is very important for lubrication of the ingesta as it passes through the intestine, particularly as more water is absorbed from the lumen making it drier.
| |
| − | *There are numerous scattered lymph nodules.
| |
| − | **The number of lymph nodules increases compared to the small intestine.
| |
| − | *The submucosa is much reduced in thickness.
| |
| − | *'''Taenia''' may be present.
| |
| − | **These are concentrations of the longitudinal muscle layer into long bands.
| |
| − | **When the taenia contract, they cause shortening of the large intestine, which produces saccualtions, or '''haustra'''.
| |
| − | *Many glands are present in the mucosa and skin of the anal region.
| |
| − | | |
| − | ==Species Differences==
| |
| − | | |
| − | ===Carnivore===
| |
| − | *The dog and cat posses two [[Anus - Anatomy & Physiology#Species Differnces|anal sacs]].
| |
| − | | |
| − | ===Ruminant===
| |
| − | | |
| − | | |
| − | ===[[Hindgut Fermenters - Horse - Anatomy & Physiology|Horse]]===
| |
| − | | |
| − | ===Pig===
| |
| − | *Taenia present
| |
| − | | |
| − | ==Links==
| |
| − | [[The Small and Large Intestines|Pathology of the Small and Large Intestine]]
| |