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Lymph Nodes, A Closer Look

Thoracic Duct

This picture shows the regions of the lymph node where the blood stream (arteries and veins) anter a typical lymph node. For the lymphatic system to function properly in its defensive role, the lymph nodes must be able to "dump" their leukocytes (infection fighting cells) quickly into the general blood stream. It is important to note that white blood cells are not produced in the Lymph nodes initially, only stored there. In the event of a serious infection (a pathogenic virus for example), the lymph nodes often become very swollen. This swelling represents the explosive multiplication of leukocyte numbers in the lymph node's honeycomb of connective tissue.

Lymph nodes can take on many different sizes and shapes, but most are bean-shaped and are around 1 inch in length. The node is covered thickly with the fibrous capsule and is subdivided into different compartments by inward pointing trabeculae. As with many organs, the lymph node has two basic parts, the cortex and the medulla. The cortex is populated mainly with lymphocytes (follicles). The germinal centers are the primary resting place for B Cell Lymphocytes (the cells responsible for production of circulating antibodies). In the event of an infecting antigen, these B Lymphocytes will rapidly undergo mitosis and divide. Each unique kind of B cell produces only one type of antibody. Thus, by dividing, they can product large quantities of a specific antibody to seek out and help destroy the antigen.

The rest of the cortex contains T lymphocytes- cells that circulate through the lymph nodes, blood stream, and lymphatic ducts to seek out any infection. The medulla of the lymph nodes is primarily made up of macrophages attached to reticular fibers.

Enlarged Bovine Lymph Node
Bovine Lymph Node

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