Library · Anatomy
Lymph node cortex
Make it clearer
The lymph node is wrapped in a capsule, and just inside it, separated only by the subcapsular sinuses, lies the cortex. That cortex is mostly home to B lymphocytes, a type of white blood cell. They are not scattered at random: they gather into lymphoid follicles, which are rounded clusters of cells.
The look of a follicle tells you whether the node has already gone to work, like an empty hall that suddenly fills with people. As long as there is no stimulus, the follicles are primary: small, all alike, with the B lymphocytes at rest. When the node responds, those follicles become secondary and a germinal center opens up inside them, surrounded by a rim called the mantle zone.
That germinal center is the workshop. There the B lymphocytes activate, multiply and differentiate, that is, they change jobs to become plasma cells or memory cells. The workshop has two halves that look different under the microscope: a dark zone, where the cells called centroblasts sit, and a light zone, where the centrocytes are.
In brief
The cortex sits just under the capsule, separated from it by the subcapsular sinuses, and it houses mostly B lymphocytes clustered into lymphoid follicles.
Without stimulation the follicles are primary: small, uniform, with resting B cells; once they respond they become secondary and develop a germinal center ringed by the mantle zone.
Inside that germinal center, B cells activate, proliferate and differentiate into plasma cells or memory cells; centroblasts fill its dark zone and centrocytes its light zone.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingHistology, Lymph Nodes, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingHistology, B-Cell Lymphocyte, StatPearlsPublished
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