View
221
Download
0
Category
Tags:
Preview:
Citation preview
Ruminant Gastro-Intestinal Tract Anatomy
Ruminant Gastro-Intestinal Tract Anatomy
Cardia
Entry of esophagus into the reticulo-rumen above the reticular fold.
Reticulum on left with honeycomb. Rumen on right with conical papillae.
Rumino-reticular foldRumino-reticular fold
Ruminant Gastro-Intestinal Tract Anatomy
Reticulum
In the adult, the reticulum comprises approximately 5% of the stomach capacity.
Pouch-like structure in the forward area of the stomach.
Tissues arranged in a network resembling a honeycomb.
Opens just below the cardia of the esophagus.
Heavy or dense feed or foreign objects eaten by the animal fall into the reticulum – hardware disease.
Ruminant Gastro-Intestinal Tract Anatomy
Reticulum ReticulumReticulum
ReticulumReticulum
The orientation of the top picture is from the right side of the animal’s body with the cranial side to the right.
The orientation of the bottom picture is from the left side of the animal’s body.
Ruminant Gastro-Intestinal Tract Anatomy
Rumen
In the adult, the rumen comprises approximately 80% of the stomach capacity.
Principle site of microbial fermentation and absorption of short-chain volatile fatty acids (VFA’s).
Absorption of VFA’s through rumen papillae which are conical or tongue shaped.
Presence of papillae increase surface area for absorption.
Venous blood from the reticulum, rumen, omasum and abomasum carries VFA’s to the portal vein and directly to the liver.
Ruminant Gastro-Intestinal Tract AnatomyRumen
Extends from diaphragm to pelvis
Divided by pillars (muscular folds) into sacs:– Dorsal sac– Ventral sac– Two caudal sacs
Ruminant Gastro-Intestinal Tract Anatomy
Rumen
Rumen papillae grow in size and number based on cellulysis. When rate of cellulysis is high, as with forage-based diets, papillae are numerous and relatively longer in length.
Mucosal pattern is unevenly distributed, reflected by the stratification of ingesta and location of fermentation.
Papillae are most numerous in the mid-level region of the rumen in the cranial sac and the dorso-caudal blindsac
Ruminant Gastro-Intestinal Tract Anatomy
Rumen Papillae
The rumen papillae are covered with stratified squamous epithelium.
Rumen papillae increase the surface area for absorption of volatile fatty acids.
Papillae are supplied by one or two arterioles
Molecules which pass through the epithelial layer of the papillae by diffusion reach the venules which transport the absorbed
material via the ruminal veins to the hepatic portal vein into the liver.
Ruminant Gastro-Intestinal Tract Anatomy
Omasum
Almost spherical compartment located to right of rumen and reticulum
Filled with muscular folds (leaves)
Also called “book-stomach”
Ruminant Gastro-Intestinal Tract Anatomy
Omasum
In the adult, comprises approximately 8% of the stomach capacity.
Globe-shaped structure containing leaves of tissue like pages in a book.
Contains similar stratified squamous epithelium to that in the rumen; highly vascularized and absorptive.
Due to folds and leaves, has 20 to 25% of the absorptive capacity of the rumen.
Ruminant Gastro-Intestinal Tract Anatomy
Omasum
Function is not well understood
Perhaps has grinding action
May absorb VFA’s
May absorb water
Reticulo-omasal orifice has a role
in regulating passage of digesta from the rumen, and thus has an influence on intake.
Ruminant Gastro-Intestinal Tract Anatomy
Abomasum
Glandular compartment of ruminant stomach, located to right of rumen, ventral to omasum.
Ruminant Gastro-Intestinal Tract Anatomy
Abomasum
In the adult, comprises approximately 7% of the stomach capacity.
Pear-shaped and curved with the wide initial portion (fundus) next to the omasum. Narrows gradually becoming the pyloric portion which is tube shaped as junctions with the small intestine
Has a glandular mucosa similar to other mammals. Glandular portion located in the fundus region. Contains HCl producing parietal cells.
Secretes the enzyme lysozyme which breaks down bacterial cell walls.
Ruminant Gastro-Intestinal Tract Anatomy
Stomach Blood Supply
Blood supply comes from the celiac artery which originates from the aorta.
The celiac artery forms six branches rather than three as in non-ruminants
Small phrenic
Hepatic – for the liver and abomasum
Several small pancreatic
Splenic which detaches to:
Right ruminal artery which is the main arterial supply of the rumen
Left ruminal artery which detaches to the reticular artery for
supply to the reticulum
Left gastric artery which supplies the remaining portions of the reticulum, omasum,and abomasum.
Ruminant Gastro-Intestinal Tract Anatomy
Stomach Blood Supply
Veins are equipped with valves and run parallel to the arteries.
There is a dense muscular, submucosal and mucosal network of blood vessels in the stomach wall, heavily developed in the prime areas
of absorption (rumen and omasum)
All venous blood from the stomach is carried to the hepatic portal vein to the liver.
Recommended