Structure: The Lymphatic System

A network of lymph vessels, lymphatic tissue, and clumps of bean-shaped lymph nodes (glands) makes up the lymphatic system. The lymph vessels collect fluid (lymph) from the body tissues and return it to the blood, maintaining the fluid balance within the body. Lymph filters through the lymph nodes, which are packed with particular types of white blood cell known as lymphocytes. These cells are produced in the bone marrow, spleen, and thymus, and they help to protect the body against infection.

Inside a lymph node

The flow of lymph slows as it moves through the narrow channels in the spaces, called sinuses, in a node. The reduction in flow allows macrophages time to filter disease organisms from the lymph.

Section of a lymph vessel

Lymph vessels have thin walls that allow fluid from the surrounding body tissues (known as lymph) to enter. The lymph is moved through the lymph vessel by the contractions of muscles. Valves in each vessel prevent backflow of fluid.

Lymphatic tissue in a node

This magnified view reveals a fine, fibrous network of lymphatic tissue. White blood cells, a key feature of the body’s immune system, are seen entangled within the mesh.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

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