2Rumino-reticular fold Ruminant Gastro-Intestinal Tract AnatomyCardiaEntry of esophagus into thereticulo-rumen above the reticular fold.Reticulum on left with honeycomb.Rumen on right with conical papillae.Rumino-reticular fold
3Ruminant Gastro-Intestinal Tract Anatomy ReticulumIn the adult, the reticulum comprises approximately 5% of thestomach capacity.Pouch-like structure in theforward area of the stomach.Tissues arranged in a networkresembling a honeycomb.Opens just below the cardia ofthe esophagus.Heavy or dense feed or foreignobjects eaten by the animal fall intothe reticulum – hardware disease.
4Ruminant Gastro-Intestinal Tract Anatomy ReticulumReticulumThe orientation of the toppicture is from the right side ofthe animal’s body with thecranial side to the right.The orientation of the bottompicture is from the left side ofthe animal’s body.Reticulum
5Ruminant Gastro-Intestinal Tract Anatomy RumenIn the adult, the rumen comprises approximately 80% of thestomach capacity.Principle site of microbial fermentationand absorption of short-chain volatilefatty acids (VFA’s).Absorption of VFA’s through rumenpapillae which are conical or tongueshaped.Presence of papillae increase surfacearea for absorption.Venous blood from the reticulum, rumen,omasum and abomasum carries VFA’sto the portal vein and directly to theliver.
6Ruminant Gastro-Intestinal Tract Anatomy RumenExtends from diaphragm to pelvisDivided by pillars (muscular folds) into sacs:Dorsal sacVentral sacTwo caudal sacs
7Ruminant Gastro-Intestinal Tract Anatomy RumenRumen papillae grow in size and number based on cellulysis.When rate of cellulysis is high,as with forage-based diets,papillae are numerous andrelatively longer in length.Mucosal pattern is unevenlydistributed, reflected by thestratification of ingesta andlocation of fermentation.Papillae are most numerous in the mid-level region of therumen in the cranial sac and the dorso-caudal blindsac
8Ruminant Gastro-Intestinal Tract Anatomy Rumen PapillaeThe rumen papillae are covered with stratifiedsquamous epithelium.Rumen papillae increase the surface areafor absorption of volatile fatty acids.Papillae are supplied by one or two arteriolesMolecules which pass through the epitheliallayer of the papillae by diffusion reach thevenules which transport the absorbedmaterial via the ruminal veins to the hepaticportal vein into the liver.
9Ruminant Gastro-Intestinal Tract Anatomy OmasumAlmost spherical compartment located to right of rumen and reticulumFilled with muscular folds (leaves)Also called “book-stomach”
10Ruminant Gastro-Intestinal Tract Anatomy OmasumIn the adult, comprises approximately 8% of the stomach capacity.Globe-shaped structurecontaining leaves of tissue likepages in a book.Contains similar stratifiedsquamous epithelium to thatin the rumen; highly vascularizedand absorptive.Due to folds and leaves, has20 to 25% of the absorptivecapacity of the rumen.
11Ruminant Gastro-Intestinal Tract Anatomy OmasumFunction is not well understoodPerhaps has grinding actionMay absorb VFA’sMay absorb waterReticulo-omasal orifice has a rolein regulating passage of digestafrom the rumen, and thus has aninfluence on intake.
12Ruminant Gastro-Intestinal Tract Anatomy AbomasumGlandular compartment of ruminant stomach, located to right of rumen, ventral to omasum.
13Ruminant Gastro-Intestinal Tract Anatomy AbomasumIn the adult, comprises approximately 7% of the stomach capacity.Pear-shaped and curved with the wide initial portion (fundus) nextto the omasum. Narrows gradually becoming the pyloric portionwhich is tube shaped as junctions with the small intestineHas a glandular mucosa similar to other mammals. Glandularportion located in the fundus region. Contains HCl producingparietal cells.Secretes the enzyme lysozyme which breaks down bacterial cellwalls.
14Ruminant Gastro-Intestinal Tract Anatomy Stomach Blood SupplyBlood supply comes from the celiac artery which originates from the aorta.The celiac artery forms six branches rather than three as in non-ruminantsSmall phrenicHepatic – for the liver and abomasumSeveral small pancreaticSplenic which detaches to:Right ruminal artery which is themain arterial supply of the rumenLeft ruminal artery which detaches to the reticular artery for supplyto the reticulumLeft gastric artery which supplies the remaining portions of thereticulum, omasum,and abomasum.
15Ruminant Gastro-Intestinal Tract Anatomy Stomach Blood SupplyVeins are equipped with valves andrun parallel to the arteries.There is a dense muscular,submucosal and mucosal network ofblood vessels in the stomach wall,heavily developed in the prime areasof absorption (rumen and omasum)All venous blood from the stomach iscarried to the hepatic portal vein to theliver.