Difference between revisions of "Abomasum - Anatomy & Physiology"

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==Introduction==
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==Overview==
 
  
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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.
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The abomasum is the fourth chamber in the ruminant. It functions similarily to the [[Monogastric Stomach - Anatomy & Physiology|carnivore stomach]] as it is glandular and functions to digest food chemically, rather than mechanically or by fermentation like the other 3 chambers of the ruminant stomach.
  
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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.
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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.
  
 
[[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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==Structure==
 
==Structure==
  
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[[Image:Abomasum Anatomy Sheep.jpg|thumb|right|250px|Abomasum Anatomy (Sheep) - Copyright RVC 2008]]
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[[Image:Abomasum Anatomy Sheep.jpg|thumb|right|150px|Abomasum Anatomy (Sheep) - Copyright RVC 2008]]
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*Lies upon the abdominal floor
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*Cranial part split into pylorus and body
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*Caudal part
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*Covered by lesser omentum
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*15-20 folds inside
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*Torus at pyloric exit
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*Outflow fairly constant
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*Motility at pylorus (peristalsis)
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*Some control at pyloric sphincter
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*Large in newborn
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*Proximal ends of the abomasal folds forms a plug preventing reflux into the [[Omasum - Anatomy & Physiology|omasum]]
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*Thin walls
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*Serousa covering
  
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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==
  
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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.
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*Chemical breakdown of food
 +
 
 +
*Secretes hydrochloric acid and pepsinogen
 +
 
 +
*Some intrinsic motility
 +
 
 +
*Impaired motility can cause distension
 +
 
 +
*Movements are slow
 +
**Contraction first of proximal part
 +
**More forceful contraction at pyloric part
 +
 
  
 
==Vasculature==
 
==Vasculature==
  
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The vasculature of the abomasum includes the '''cranial mesenteric artery''', the '''celiac artery''' and the '''left gastric''' and '''left gastroepiploic''' arteries.
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*Cranial mesenteric artery
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*Celiac artery
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*Left gastric and left gasrtoepiploic arteries
 +
 
  
 
==Innervation==
 
==Innervation==
  
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The innervation of the abomasum includes the '''dorsal vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) and the '''ventral vagus nerve''' ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important).
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*Dorsal vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]])  
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*Ventral vagus nerve ([[Cranial Nerves - Anatomy & Physiology|CN X]]) (most important)
  
 
==Lymphatics==
 
==Lymphatics==
  
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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 - Anatomy & Physiology|omasum]]''', then to the hepatic lymph nodes.
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*Single lymph nodules are present at the junction between epithelium and lamina propria
  
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==Histology==
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*Numerous small lymph nodes are scattered in the abomasal curvatures
  
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[[Image:Abomasum Histology Sheep.jpg|thumb|right|150px|Abomasum Histology (Sheep) - Copyright RVC 2008]]
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*The lymph drains to larger atrial nodes between the cardia and [[Omasum - Anatomy & Physiology|omasum]], then to the hepatic lymph nodes
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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.
 
  
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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.
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==[[Abomasum - Histology|Histology]]==
  
 
==Species Differences==
 
==Species Differences==
  
 
===Small Ruminants===
 
===Small Ruminants===
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The abomasum can contact the [[Liver - Anatomy & Physiology|liver]]. The abomasum is proportionately larger than in cattle.
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*Abomasum can contact [[Liver - Anatomy & Physiology|liver]]
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*Abomasum is proportionately larger than in cattle
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==Test yourself with the stomach of ruminants flashcards==
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[[The Stomachs of the Ruminant - Anatomy & Physiology - Flashcards#The Abomasum|The Abomasum Flashcards]]
  
 
==Links==
 
==Links==
  
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'''Click here for [[Rumen - Anatomy & Physiology|Rumen - Anatomy & Physiology]]'''
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[[Rumen - Anatomy & Physiology|The Rumen - Anatomy & Physiology]]
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[[Reticulum - Anatomy & Physiology|The Reticulum - Anatomy & Physiology]]
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[[Omasum - Anatomy & Physiology|The Omasum - Anatomy & Physiology]]
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'''Video'''
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[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Pot 52 Lateral view of the Abdomen of a young Ruminant]
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[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Pot 175 Sections of the Ruminant Stomach]
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[http://stream2.rvc.ac.uk/Anatomy/ovine/Pot0047.mp4 Pot 47 Ovine Omasum and Abomasum]
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[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]
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[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]
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[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
  
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'''Click here for [[Reticulum - Anatomy & Physiology|Reticulum - Anatomy & Physiology]]'''
 
  
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'''Click here for [[Omasum - Anatomy & Physiology|Omasum - Anatomy & Physiology]]'''
 
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<br><br>
 
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{{Learning
 
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|flashcards = [[Abomasum Flashcards]]
 
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<!-----|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0052.mp4 Lateral view of the Abdomen of a young Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/pot0175.mp4 Sections of the Ruminant Stomach]<br>[http://stream2.rvc.ac.uk/Anatomy/ovine/Pot0047.mp4 Ovine Omasum and Abomasum]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]---->
 
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|powerpoints = [[Ruminant Gastrointestinal Tract Histology resource|Histology of the ruminant gastrointestinal tract]]
 
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}}
 
  
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==Webinars==
 
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<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
 
 
[[Category:Stomach - Anatomy & Physiology]]
 
[[Category:Stomach - Anatomy & Physiology]]
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[[Category:A&P Done]]
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[[Category:To Do - A&P]]
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[[Category:Alimentary Anatomy - Cattle]]
 

Revision as of 13:36, 9 September 2010

Introduction

The abomasum is the fourth chamber in the ruminant. It functions similarily to the carnivore stomach as it is glandular and functions to digest 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.

Displacement of the abomasum to the left or to the right is a common disorder affecting dairy cows due to high concentrate feed.


Structure

Abomasum Anatomy (Sheep) - Copyright RVC 2008
  • Lies upon the abdominal floor
  • Cranial part split into pylorus and body
  • Caudal part
  • Covered by lesser omentum
  • 15-20 folds inside
  • Torus at pyloric exit
  • Outflow fairly constant
  • Motility at pylorus (peristalsis)
  • Some control at pyloric sphincter
  • Large in newborn
  • Proximal ends of the abomasal folds forms a plug preventing reflux into the omasum
  • Thin walls
  • Serousa covering


Function

  • Chemical breakdown of food
  • Secretes hydrochloric acid and pepsinogen
  • Some intrinsic motility
  • Impaired motility can cause distension
  • Movements are slow
    • Contraction first of proximal part
    • More forceful contraction at pyloric part


Vasculature

  • Cranial mesenteric artery
  • Celiac artery
  • Left gastric and left gasrtoepiploic arteries


Innervation

  • Dorsal vagus nerve (CN X)
  • Ventral vagus nerve (CN X) (most important)

Lymphatics

  • Single lymph nodules are present at the junction between epithelium and 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

Species Differences

Small Ruminants

  • Abomasum can contact liver
  • Abomasum is proportionately larger than in cattle

Test yourself with the stomach of ruminants flashcards

The Abomasum Flashcards

Links

The Rumen - Anatomy & Physiology

The Reticulum - Anatomy & Physiology

The Omasum - Anatomy & Physiology

Video

Pot 52 Lateral view of the Abdomen of a young Ruminant

Pot 175 Sections of the Ruminant Stomach

Pot 47 Ovine Omasum and Abomasum

Left sided topography of the Ovine Abdomen and Thorax

Right sided topography of the Ovine Abdomen

Structure of the ruminant forestomachs

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