Normal Anatomy, Histology, Immunohistology, and Ultrastructure, Lymph Node, Rat

Abstract

The lymph nodes of the rat are small, round, or kidney–shaped organs with a length of 3–5 mm which can be distinguished from the surrounding fat by their pearly gloss. They occur dispersed throughout the body, always connected with lymph vessels. Particularly in the axillar, inguinal, and cervical regions, along the larger arteries, and within the mesenterium, groups of nodes can be found (Fig. 124; Tilney 1971). The nodes are surrounded by a fibrous capsule from which trabeculae emerge. At the convex side thin afferent lymph vessels are recognizable, at the concave side (the hilus) small arteries and nerves supply the node, and the efferent lymph vessels and veins leave the node. The lymph vessels possess small valves to force the lymph stream in one direction. Though there are small variations between the different lymph nodes, in general the architecture is about the same. On cross section the cortex with small white nodules can be discriminated from the centrally located medulla. As an exception to the regular nodes, the renal nodes are reddish, due to the large numbers of red blood cells within the medullary region; these nodes are designated as hemolymph nodes (Andreasen and Gottlieb 1946). Like all other lymph nodes these nodes are interposed in the lymphatic stream and thus possess normal afferent and efferent lymph vessels (Kazeem et al. 1982).