The lymphatic channels of the body drain into groups of that are strategically placed to filter the lymph draining body regions and to provide immune surveillance based upon the antigen content of the lymph. The afferent lymphatic channels drain into the periphery of a lymph node in a region under the connective tissue capsule known as the subcapsular sinus. In the periphery of a lymph node is the paracortical region where lymphoid follicles are located. A follicle is a loosely arranged structure with an outer mantle of small T lymphocytes and agerminal center composed of B lymphocytes, follicular dendritic cells, and macrophages. The interfollicular zones between the follicles are populated mainly by T cells. From the periphery of the node, connective tissue trabeculae extend toward the hilum of the node. Sinuses drain toward the hilum and contain mainly macrophages. The medullary cords located near the hilum of the node contain mainly plasma cells and small lymphocytes. From the hilum, the efferent lymphatic channels egress.

The structure of a lymph node is diagrammed above:

  • A - Afferent lymphatic channels

  • B - Subcapsular sinus

  • C - Follicle

  • D - Sinuses

  • E - Paracortical region

  • F - Medullary cords

  • G - Efferent lymphatic channel