25.7 : 淋巴结的详细结构和功能

Lymph nodes are small, bean-shaped structures that cluster along the lymphatic vessels. They are majorly located in the inguinal, axillary, and cervical regions.

These nodes have an outer covering called the capsule, which extends trabeculae inward, dividing the node into compartments.

Histologically, each lymph node can be divided into superficial cortex and deep medulla.

The cortex comprises dendritic cells, macrophages, and densely packed follicles of B lymphocytes. Upon antigen presentation by dendritic cells, the B-lymphocytes mature into antibody-producing plasma cells and memory B cells.

The inner cortex mainly consists of T-lymphocytes migrated from the cortex. It also contains dendritic cells, which can activate the T-lymphocytes.

Lymph enters the lymph nodes via afferent lymphatics and flows through sinuses filled with reticular fibers, lymphocytes, and macrophages.

Lymph gets filtered within these sinuses. Macrophages eliminate foreign substances through phagocytosis, while lymphocytes destroy pathogens using immune responses.

The filtered lymph leaves the lymph node via efferent lymphatics and emerges from the other end of the node at the hilum.