Figure 1319

Photomicrograph of a lymph node. This silver preparation shows the connective tissue capsule (at the top), subcapsular sinus, and the superficial cortex of the lymph node (at the bottom). The reticular fibers (arrows) form an irregular anastomosing network throughout the stroma of the lymph node. Note elongated oval nuclei of reticular cells (arrowheads), which are in intimate contact with reticular fibers in the sinus. X640.

on the thymus, perinatal thymectomy in animals results in a poorly developed deep cortex. On the basis of this observation, the deep cortex is also called the thymus-clependent cortex.

The medulla of the lymph node consists of the medullary cords and medullary sinuses

The medulla, the inner part of the lymph node, consists of cords of lymphatic tissue separated by lymphatic sinuses called medullary sinuses. As described above, a network of reticular cells and fibers traverses the medullary cords and medullary sinuses and serves as the framework of the parenchyma. In addition to reticular cells, the medullary cords contain lymphocytes (mostly B lymphocytes), macrophages, and plasma cells. The medullary sinuses converge near the hilum, where they drain into efferent lymphatic vessels.

Filtration of lymph in the lymph node occurs within a network of interconnected lymphatic channels called sinuses

There are three types of lymphatic channels called sinuses in the lymph node. Just beneath the capsule of the lymph node is a sinus interposed between the capsule and the cortical lymphocytes called the subcapsular sinus or cortical sinus. Afferent lymphatic vessels drain lymph into this sinus. Trabecular sinuses that originate from the subcapsular sinuses extend through the cortex along the tra-beculae and drain into medullary sinuses. Lymphocytes and macrophages or their processes readily pass back and forth between the lymphatic sinuses and the parenchyma

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