The arterial supply to lymph nodes in sheep.

The aim of this study was to describe how lymph nodes in sheep receive their blood supply, and to provide some information on the pathways followed by arteries and their branches within the nodes. It was found that considerable variation exists in the arterial supply to lymph nodes in sheep. Each node may receive branches from one, two or three major arteries; the nodes may be up to 10-15 cm from these arteries, but some arteries actually pass through lymph nodes. Most branches enter at a hilus, which varies in shape, size and location, but some penetrate the capsule directly. Within the node, arteries may either proceed directly towards the cortex or extend longitudinally through the medulla; in each case branches are given off to supply the medulla and, in greater numbers, the cortex. Some arteries then leave the node through the capsule and either supply perinodal fat and/or more distal structures, or join other arteries. Anastomoses may also occur before the arteries enter a node, or within the node or at its surface. These direct anastomoses and arterial circles could play a part in maintaining the blood supply to a node when it is being bombarded with microorganisms and inflammatory products from an area of infection.