INTRAMURAL VASCULAR SYSTEM OF THE LARGE-I NTESTINE OF DOMESTIC RUMINANTS

The vascular system of the large intestine of 15 cattle, 10 sheep and 5 goats has been examined by means of corrosion vascular casts, histol ogy and electron microscopy. The results are as follows: The course an d ramification of the intestinal vessels are identical in the caecum, colon and rectum. Furthermore, as expected, amongst the species studie d no substantial differences in the vascular architecture of the large intestinal wall could be determined. The extramural vessels reach the wall of the intestine at the mesenteric margin. Their branches build arterial or venous networks in the tela subserosa, which then divide i nto branches in the direction of the antimesenteric region. The connec tions between the blood vessels of the tela subserosa and the tela sub mucosa as well as the branches to the muscular layers emerge from thes e networks. In the tela submucosa an arterial and venous system can be found. The obvious vascular arrangement in the submucosa is arranged not only parallel to the stratum circulare of the tunica muscularis bu t also along the prevailing direction of the lamina muscularis mucosae . From this arrangement both a deep and a superficial submucosal vascu lar plexus can be denominated. The recurrent branches for the circular muscle layer as well as the afferent and efferent Vessels of the muco sa originate from submucosal arteries and veins. The arterioles of the tunica mucosa branch at the level of the basal crypts into a periglan dular capillary system running close to the lumen into a subepithelial capillary system. Here the capillaries drain into venules which advan ce to the region of the intestinal glands and consequently drain into collecting veins in the submucosa. Capillaries of the subepithelial la mina propria mucosae are furnished with continuous or fenestrated endo thelial linings as the morphological equivalent of the secretory or re sorption processes, respectively. In the walls of the large intestine of the bovine, sheep and goat there are neither arterio-venous anastom oses nor hemodynamic regulatory structures such as sphincters or so-ca lled throttle veins at the points of transition from capillaries to ve nules. These results are in accord with the findings in the small inte stine of domestic ruminants (Hummel 1980).