Page 441 - Atlas of Histology with Functional Correlations

The lymph node consists of lymphocyte aggregations intermixed with dilated

lymphatic sinuses that contain lymph and are supported by a framework of fine
reticular fibers. A lymph node cut in half shows the outer dark-staining cortex
(4) and the inner light-staining medulla (10). The lymph node is surrounded by a
pericapsular adipose tissue (1) with numerous blood vessels (9). A dense
connective tissue capsule (2) surrounds the lymph node. From the capsule (2),

connective tissue trabeculae (6) extend into the node, initially between the
lymphatic nodules and then throughout the medulla (10). The trabecular
connective tissue (6) also exhibits the major blood vessels (5, 8).

Afferent lymphatic vessels with valves (7) course in the connective tissue

capsule (2) of the lymph node and, at intervals, penetrate the capsule to enter a
narrow subcapsular sinus (3, 15). From here, the sinuses (cortical sinuses)
extend along the trabeculae (6) into the medullary sinuses (11).

The lymph node cortex (4) contains numerous lymphocyte aggregations
called lymphatic nodules (16). Some nodules (16) exhibit a lighter-stained area

in their center. These are the germinal centers (17) of the lymphatic nodules
(16) and represent the sites of active lymphocyte proliferation.

In the medulla (10) of the lymph node, the lymphocytes are arranged as
irregular cords of lymphatic tissue called medullary cords (14) that contain

macrophages, plasma cells, and small lymphocytes. The dilated medullary
sinuses (11) drain the lymph from the cortical region of the lymph node and
course between the medullary cords (14) toward the concavity of the lymph
node, the hilus (12).

Nerves, blood vessels, and veins that supply and drain the lymph node are

located in the hilus (12). Efferent lymphatic vessels (13) drain the lymph from
the medullary sinuses (11) and exit the lymph node in the hilus (12).

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