Difference between revisions of "Abomasum - Anatomy & Physiology"
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==Overview== | ==Overview== | ||
| − | The '''abomasum''' is the fourth chamber in the ruminant. It functions | + | The '''abomasum''' is the fourth chamber in the ruminant. It functions similarly to the [[Monogastric Stomach - Anatomy & Physiology|carnivore stomach]] as it is glandular and digests food chemically, rather than mechanically or by fermentation like the other 3 chambers of the ruminant stomach. |
| − | The '''abomasum''' differs in its position within the abdomen, depending on fullness of the other chambers of the stomach, intrinsic abomasonal activity, contractions of the '''[[Rumen - Anatomy & Physiology|rumen]]''' and '''[[Reticulum - Anatomy & Physiology|reticulum]]''' (to which it is attached) and by age and pregnancy. | + | The '''abomasum''' differs in its position within the abdomen, depending on fullness of the other chambers of the stomach, intrinsic abomasonal activity, contractions of the '''[[Rumen - Anatomy & Physiology|rumen]]''' and '''[[Reticulum - Anatomy & Physiology|reticulum]]''' (to which it is attached) and by age and pregnancy status. |
[[Displaced Abomasum|Displacement of the abomasum]] to the left or to the right is a common disorder affecting dairy cows due to high concentrate feed. | [[Displaced Abomasum|Displacement of the abomasum]] to the left or to the right is a common disorder affecting dairy cows due to high concentrate feed. | ||
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[[Image:Abomasum Anatomy Sheep.jpg|thumb|right|250px|Abomasum Anatomy (Sheep) - Copyright RVC 2008]] | [[Image:Abomasum Anatomy Sheep.jpg|thumb|right|250px|Abomasum Anatomy (Sheep) - Copyright RVC 2008]] | ||
| − | The '''abomasum''' lies upon the abdominal floor. The cranial part is split into the '''pylorus''' and '''body'''. There is also a caudal part. It is covered by the '''lesser omentum'''. It has 15-20 folds inside. The '''torus''' is at the pyloric exit. The outflow is fairly constant. There is motility at the '''pylorus''' (peristalsis) | + | The '''abomasum''' lies upon the abdominal floor. The cranial part is split into the '''pylorus''' and '''body'''. There is also a caudal part. It is covered by the '''lesser omentum'''. It has 15-20 folds inside. The '''torus''' is at the pyloric exit. The outflow is fairly constant. There is motility at the '''pylorus''' (peristalsis) and some control at the '''pyloric sphincter'''. The abomasum is large in newborn animals. The proximal ends of the abomasal folds form a plug preventing reflux into the '''[[Omasum - Anatomy & Physiology|omasum]]'''. It has thin walls and a serosa covering. |
==Function== | ==Function== | ||
| − | The function of the abomasum is the chemical breakdown of food. It secretes hydrochloric acid and pepsinogen. It has some intrinsic motility. Impaired motility can cause distension. The movements are slow, contractions occur first in the proximal part and are more forceful at the pyloric part. | + | The function of the abomasum is the chemical breakdown of food. It secretes '''hydrochloric acid''' and '''pepsinogen'''. It has some intrinsic motility. Impaired motility can cause distension. The movements are slow, contractions occur first in the proximal part and are more forceful at the pyloric part. |
==Vasculature== | ==Vasculature== | ||
| − | The vasculature of the abomasum includes the '''cranial mesenteric artery''', the '''celiac artery''' and the '''left gastric''' and '''left | + | The vasculature of the abomasum includes the '''cranial mesenteric artery''', the '''celiac artery''' and the '''left gastric''' and '''left gastroepiploic''' arteries. |
==Innervation== | ==Innervation== | ||
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[[Image:Abomasum Histology Sheep.jpg|thumb|right|150px|Abomasum Histology (Sheep) - Copyright RVC 2008]] | [[Image:Abomasum Histology Sheep.jpg|thumb|right|150px|Abomasum Histology (Sheep) - Copyright RVC 2008]] | ||
| − | The abomasum has a simple columnar epithelium. There are 3 layers of '''tunica muscularis'''- inner oblique, middle circular and outer longitudinal. The '''lamina muscularis''' is thicker and has 3 separate layers. | + | The abomasum has a simple columnar epithelium. There are 3 layers of '''''tunica muscularis''''' - inner oblique, middle circular and outer longitudinal. The '''''lamina muscularis''''' is thicker and has 3 separate layers. |
| − | Gastric glands are present in the '''lamina propria''' of the mucosal layer in the pyloric region | + | Gastric glands are present in the '''''lamina propria''''' of the mucosal layer in the pyloric region (lighter part). The abomasum is heavily coated by mucous for protection. The submucosa contains loose connective tissue, many blood vessels and unilocular adipocytes. The coiled glands in the ''lamina propria'' open into deep gastric pits. The inner mucosa is pink. '''Rugae''' are present in the pyloric region and a '''torus''' (large swelling) is present at the pyloric passage to narrow the lumen. The dark mucosa of the fundus and body contains peptic glands. |
==Species Differences== | ==Species Differences== | ||
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[[Category:Stomach - Anatomy & Physiology]] | [[Category:Stomach - Anatomy & Physiology]] | ||
| − | [[Category: | + | [[Category:A&P Done]] |
Revision as of 14:47, 17 December 2010
Overview
The abomasum is the fourth chamber in the ruminant. It functions similarly to the carnivore stomach as it is glandular and digests food chemically, rather than mechanically or by fermentation like the other 3 chambers of the ruminant stomach.
The abomasum differs in its position within the abdomen, depending on fullness of the other chambers of the stomach, intrinsic abomasonal activity, contractions of the rumen and reticulum (to which it is attached) and by age and pregnancy status.
Displacement of the abomasum to the left or to the right is a common disorder affecting dairy cows due to high concentrate feed.
Structure
The abomasum lies upon the abdominal floor. The cranial part is split into the pylorus and body. There is also a caudal part. It is covered by the lesser omentum. It has 15-20 folds inside. The torus is at the pyloric exit. The outflow is fairly constant. There is motility at the pylorus (peristalsis) and some control at the pyloric sphincter. The abomasum is large in newborn animals. The proximal ends of the abomasal folds form a plug preventing reflux into the omasum. It has thin walls and a serosa covering.
Function
The function of the abomasum is the chemical breakdown of food. It secretes hydrochloric acid and pepsinogen. It has some intrinsic motility. Impaired motility can cause distension. The movements are slow, contractions occur first in the proximal part and are more forceful at the pyloric part.
Vasculature
The vasculature of the abomasum includes the cranial mesenteric artery, the celiac artery and the left gastric and left gastroepiploic arteries.
Innervation
The innervation of the abomasum includes the dorsal vagus nerve (CN X) and the ventral vagus nerve (CN X) (most important).
Lymphatics
Single lymph nodules are present at the junction between the epithelium and the lamina propria. Numerous small lymph nodes are scattered in the abomasal curvatures. The lymph drains to larger atrial nodes between the cardia and omasum, then to the hepatic lymph nodes.
Histology
The abomasum has a simple columnar epithelium. There are 3 layers of tunica muscularis - inner oblique, middle circular and outer longitudinal. The lamina muscularis is thicker and has 3 separate layers.
Gastric glands are present in the lamina propria of the mucosal layer in the pyloric region (lighter part). The abomasum is heavily coated by mucous for protection. The submucosa contains loose connective tissue, many blood vessels and unilocular adipocytes. The coiled glands in the lamina propria open into deep gastric pits. The inner mucosa is pink. Rugae are present in the pyloric region and a torus (large swelling) is present at the pyloric passage to narrow the lumen. The dark mucosa of the fundus and body contains peptic glands.
Species Differences
Small Ruminants
The abomasum can contact the liver. The abomasum is proportionately larger than in cattle.
Links
Test yourself with the Abomasum Flashcards
Click here for Rumen - Anatomy & Physiology
Click here for Reticulum - Anatomy & Physiology
Click here for Omasum - Anatomy & Physiology
Video links:
1.Pot 52 Lateral view of the Abdomen of a young Ruminant
2.Pot 175 Sections of the Ruminant Stomach
3.Pot 47 Ovine Omasum and Abomasum
4.Left sided topography of the Ovine Abdomen and Thorax