VSR 421: Regional Veterinary Surgery (2+1)

A REVIEW OF ANATOMY

• In bovines and small ruminants, the compound stomach occupies approximately three fourth of the abdominal cavity and almost fills the left half of it.
• The rumen, reticulum and omasum are regarded as oeosphageal sacculations and are lined with stratified squamous epithelium.
• The abomasum has a glandular mucous membrane. Hence it is also called true stomach.
• The reticulum is the smallest compartment of the stomach in bovines while the omasum is the smallest in sheep.
• The long axis of the rumen extends from a point opposite to the ventral part of the 7^th or 8^th intercostals space almost to the pelvic inlet.
• The parietal surface is related to the diaphragm, spleen and the left and ventral abdominal wall.
• The visceral surface is related to the liver, omasum, abomasum, pancreas, intestine, left kidney and left adrenal. The surface of the rumen are marked by the right and left grooves which extremely separate the dorsal and ventral sacs.
• The rumeno reticular groove demarcates the reticulum from the dorsal sac on the left side. The mucous membrane of the rumen is brown in colour and free from glands. The rumen papillae cover the mucosa to provide a grip over the ingesta during rumen contractions.
• The reticulum lies between the sixth to 8^th or 9^th inter costal space and almost equal parts lie on either side of the median line.
• The mucous membrane of the reticulum is raised into folds in a typical honey comb pattern and acts like a sieve for foreign bodies.
• The reticular groove starts at the cardia to connect it with the abomasums and its length is about 15 to 20 cm in bovines and 7 to 10 cm in small ruminants.
• The muscular lips of the groove encircle the cardia from dorsal aspect and pass steeply down the reticular wall in the direction of reticulo-omasal opening in young ruminants, the reticular groove closes when the animal drinks milk so that the liquid passes directly to the abomasums.
• Receptors to initiate thin reflex are located in the larynx. As the animal grows, the reflex weakens and finally both solids and fluids are deposited in the cranial sac of the rumen.
• The reticulo omasal orifice lies 12-15cm above the bottom of the reticulum in the lesser curvature. In bovines, the omasum is mainly located on the right side of the median plane opposite to the 7^th to 11^th intercostal spaces reaching up to a hand breadth below the costal arch. In small ruminants, the omasum occupies the position between 8^th and 10^th intercostals spaces and does not come in contact with the right body wall.
• The cavity of the omasum is occupied by longitudinal folds into which food is passed in thin layers and reduced to a fine state by round horny papillae which occupy the surfaces of the folds.
• The omasal groove extends from the reticuloomasal opening to the omaso-abomasal opening and is about 10cm long.