A lymph node or lymph gland is an ovoid or kidney-shaped organ of the lymphatic system and the adaptive immune system. Lymph nodes are widely present throughout the body and are linked by the lymphatic vessels. They are major sites of B and T cells and other white blood cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles and cancer cells, but they do not have a detoxification function.

In the lymphatic system a lymph node is a secondary lymphoid organ. A lymph node is enclosed in a fibrous capsule and is made up of an outer cortex and an inner medulla.

Lymph nodes become inflamed or enlarged in various diseases, which may range from trivial throat infections to life-threatening cancers. The condition of lymph nodes is very important in cancer staging, which decides the treatment to be used and determines the prognosis. Lymphadenopathy refers to glands that are enlarged or swollen. When inflamed or enlarged, lymph nodes can be firm or tender.

Lymph nodes are kidney or oval shaped and range in size from 0.1 to 2.5 cm long. Each lymph node is surrounded by a fibrous capsule, which extends inside a lymph node to form trabeculae.The substance of a lymph node is divided into the outer cortex and the inner medulla.These are rich with cells.The hilum is an indent on the concave surface of the lymph node where lymphatic vessels leave and blood vessels enter and leave.

Lymph enters the convex side of a lymph node through multiple afferent lymphatic vessels and from here flows into a series of sinuses. After entering the lymph node from afferent lymphatic vessels, lymph flows into a space underneath the capsule called the subcapsular sinus, then into cortical sinuses. After passing through the cortex, lymph then collects in medullary sinuses.All of these sinuses drain into the efferent lymph vessels to exit the node at the hilum on the concave side.

Lymph nodes are present throughout the body, are more concentrated near and within the trunk, and are divided in the study of anatomy into groups.There are about 450 lymph nodes in the adult.Some lymph nodes can be felt when enlarged (and occasionally when not), such as the axillary lymph nodes under the arm, the cervical lymph nodes of the head and neck and the inguinal lymph nodes near the groin crease. Most lymph nodes lie within the trunk adjacent to other major structures in the body - such as the paraaortic lymph nodes and the tracheobronchial lymph nodes.

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Journal of Phlebology and Lymphology
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