First description and morphology of haemal nodes in piglets (Sus scrofa domestica).

In this study, the presence of haemal nodes, previously recognised especially in ruminants, was determined for the first time in piglets. The morphology of haemal nodes located in the abdominal cavity of seven piglets was studied by gross inspection and by histological methods. Haemal nodes reddish in colour and oval or round in shape were observed on the thin branches originating from the caudal and cranial mesenteric arteries. These nodes, having connection only with blood vessels, were covered with a thin connective tissue capsule. The haemal nodes had a hilus at the entrance of which large blood vessels were seen. These blood vessels extended into the inside of the nodes through trabeculae. Afferent and efferent lymph vessels were not observed in the haemal nodes. The nodes contained many sinuses formed by reticular fibres and reticular cells and filled by red blood cells. In the haemal nodes, lymphocytic infiltration was more commonly seen than lymph follicles.