Lymph node

Small, bean-shaped organs of the lymphatic system

A lymph node is a small, bean-shaped structure that is part of the body's lymphatic system. Lymph nodes are distributed widely throughout the body and are linked by lymphatic vessels. They are major sites of B cell and T cell lymphocytes, and other white blood cells. Lymph nodes act as filters for foreign particles and cancer cells.

Structure

Lymph nodes are small, soft, round or oval structures that are usually not palpable. They are located along the lymphatic vessels and are most densely clustered in the neck, armpits, and groin. Each lymph node is surrounded by a fibrous capsule, which extends inside the node to form trabeculae. The internal structure of a lymph node is divided into the outer cortex and the inner medulla.

Cortex

The cortex is the outer part of the lymph node and contains follicles, which are collections of lymphocytes. The follicles can be primary or secondary, with secondary follicles having a germinal center where B cells proliferate and differentiate.

Medulla

The medulla is the inner part of the lymph node and contains medullary cords, which are extensions of the cortex. The medullary cords contain lymphocytes, plasma cells, and macrophages. The medullary sinuses are spaces that allow lymph to flow through the node.

Function

Lymph nodes play a crucial role in the body's immune response. They filter lymph, trapping bacteria, viruses, and other foreign substances, which are then destroyed by specialized white blood cells called lymphocytes. Lymph nodes also produce lymphocytes, which are essential for the immune response.

Immune Response

When an antigen is detected in the lymph, it is presented to lymphocytes in the lymph node. This triggers an immune response, leading to the activation and proliferation of lymphocytes. Activated B cells can differentiate into plasma cells that produce antibodies, while T cells can directly attack infected cells.

Clinical Significance

Lymph nodes can become swollen due to infections, inflammation, or cancer. Swollen lymph nodes, or lymphadenopathy, can be a sign of various conditions, ranging from minor infections to serious diseases like lymphoma or metastatic cancer.

Lymphadenopathy

Lymphadenopathy refers to the enlargement of lymph nodes. It can be localized, affecting nodes in a specific area, or generalized, affecting nodes throughout the body. Causes of lymphadenopathy include infections, autoimmune diseases, and malignancies.

Lymphoma

Lymphoma is a type of cancer that originates in the lymphatic system, particularly in the lymph nodes. It is classified into Hodgkin lymphoma and non-Hodgkin lymphoma, each with distinct characteristics and treatment approaches.

Related pages

• Lymphatic system
• Immune system
• Lymphocyte
• Lymphoma
• Lymphadenopathy