Venous outflow system in rabbit gastric mucosa.

The purpose of this work was to compare the organisation of the gastric mucosal venous system in larger animals, exemplified by rabbits, with that of the rat and the hamster which we have described previously. Rabbits were given atropine and hexamethonium followed by intravital ligation of all veins draining the stomach, causing strong hyperaemia. The distribution of vessels was studied in the non-mounted mucosa, in mounts of mucosa cleared in light mineral oil and in paraffin or semi-thin plastic sections. We found that blood from rabbit gastric mucosa is drained by collecting venules, running from the subepithelial layer towards the muscularis mucosae. The collecting venules join the paramuscular vessels parallel and adjacent to the muscularis mucosae. Neighbouring venules form numerous arcade-like connections and gradually enlarge. Two venules and an arteriole form triplets initially situated at the luminal face of the muscularis mucosae and gradually passing onto its abluminal surface. In rats vascular triplets were absent and the collecting venules drained into paramuscular vessels joining submucosal veins. In hamsters both connections between paramuscular vessels and submucosal veins and the passing of vascular triplets across muscularis mucosae were observed. Contraction/relaxation of the muscularis mucosae may regulate the amount of blood in the venous system of the mucosa and change the intramucosal pressure, affecting movement of the tissue fluid and, indirectly, the function of the gastric cells.