STRUCTURE AND VENOUS VASCULAR BED OF THE RECTUM IN STAVROPOL BREED SHEEP

This investigation was aimed at the study of macromorphology of the rectum, including its intramural and extraorgan venous vascular bed in 18-month-old sheep of Stavropol breed. The methods used included anatomical preparation, morphometry, contrast mass intravascular injection, separation of an intestinal wall into the individual layers and preparation of total samples. The thickness of rectal muscular coat in 18-month-old sheep was found to increase in the caudal direction which is interpreted as an adaptation of the intestine for the evacuation of condensed fecal masses through the anal canal lumen. Intramural rectal venous vascular bed included three plexuses: submucosal, muscular and subserosal. The prevalence of the veins of wide-field type with an index of 90–120 in the rectal wall of a sheep results in the deceleration of the venous blood flow in the organ. At the same time, rectal intramural venous vascular bed possesses higher adaptive capacity in the cases of occlusion of the basic roots due to the well developed collateral network located between the roots of wide-field veins. The major extraorgan venous vessel of sheep rectum is a cranial rectal vein. Presence of its terminoterminal anastomoses with caudal rectal and left colonic veins may provide a bypass rectal venous blood flow in the cases of a the obstruction of one of its major vessels of various etiology.

rectum, venous vascular bed, anastomoses, vascular plexus, sheep