Difference between revisions of "Abomasum - Anatomy & Physiology"

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==Introduction==
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The abomasum is the fourth chamber in the ruminant. It functions similarily to the [[Forestomach - 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 [[The Rumen - Anatomy & Physiology|rumen]] and [[The Reticulum - Anatomy & Physiology|reticulum]] (to which it is attached) and by age and pregnancy.
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[[Stomach and Abomasum Physical Disruptions - Pathology#Displaced Abomasum in the Cow|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==
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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 [[The Omasum - Anatomy & Physiology|omasum]]
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*Thin walls
 +
 +
*Serousa covering
 +
 +
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==Function==
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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
 +
 +
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==Vasculature==
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*Cranial mesenteric artery
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*Celiac artery
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*Left gastric and left gasrtoepiploic arteries
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==Innervation==
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*Dorsal vagus nerve ([[Nervous System - CNS - Anatomy & Physiology#Innervation - Cranial Nerves|CN X]])
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*Ventral vagus nerve ([[Nervous System - CNS - Anatomy & Physiology#Innervation - Cranial Nerves|CN X]]) (most important)
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==Lymphatics==
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*Single lymph nodules are present at the junction between epithelium and lamina propria
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*Numerous small lymph nodes are scattered in the abomasal curvatures
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*The lymph drains to larger atrial nodes between the cardia and [[The Omasum - Anatomy & Physiology|omasum]], then to the hepatic lymph nodes
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==Histology==
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[[Image:Abomasum Histology Sheep.jpg|thumb|right|150px|Abomasum Histology (Sheep) - Copyright RVC 2008]]
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*Simple columnar epithelium
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*3 layers of tunica muscularis- inner oblique, middle circular and outer longitudinal
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*Lamina muscularis thicker (3 separate layers)
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*Gastric glands in lamina propria of mucosal layer in pyloric region (lighter part)
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*Heavily coated by mucous for protection
 +
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*Submucosa contains loose connective tissue, many blood vessels and unilocular adipocytes
 +
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*Deep gastric pits
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*Coiled glands in lamina propria opening into gastric pits
 +
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*Pink inner mucosa
 +
 +
*Rugae are present in the pyloric region
 +
 +
*Torus (large swelling) is present at the pyloric passage to narrow the lumen
 +
 +
*Dark mucosa of fundus and body contain peptic glands
 +
 +
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==Species Differences==
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===Small Ruminants===
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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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==Links==
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[[The Rumen - Anatomy & Physiology|The Rumen - Anatomy & Physiology]]
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[[The Reticulum - Anatomy & Physiology|The Reticulum - Anatomy & Physiology]]
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[[The Omasum - Anatomy & Physiology|The Omasum - Anatomy & Physiology]]
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[[The Stomachs of the Ruminant - Anatomy & Physiology - Flashcards#The Abomasum|The Abomasum Flashcards]]
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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]

Revision as of 23:26, 25 August 2008

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()Map ALIMENTARY SYSTEM (Map)



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

Abomasum Histology (Sheep) - Copyright RVC 2008
  • Simple columnar epithelium
  • 3 layers of tunica muscularis- inner oblique, middle circular and outer longitudinal
  • Lamina muscularis thicker (3 separate layers)
  • Gastric glands in lamina propria of mucosal layer in pyloric region (lighter part)
  • Heavily coated by mucous for protection
  • Submucosa contains loose connective tissue, many blood vessels and unilocular adipocytes
  • Deep gastric pits
  • Coiled glands in lamina propria opening into gastric pits
  • Pink inner mucosa
  • Rugae are present in the pyloric region
  • Torus (large swelling) is present at the pyloric passage to narrow the lumen
  • Dark mucosa of fundus and body contain peptic glands


Species Differences

Small Ruminants

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

Links

The Rumen - Anatomy & Physiology

The Reticulum - Anatomy & Physiology

The Omasum - Anatomy & Physiology

The Abomasum Flashcards

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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