What Are Lymph Nodes Filled With?

Lymph nodes are small oval-shaped structures of lymphatic tissue, 0.1–2.5 cm long, distributed broadly all over the body & connected to each other by the lymphatic vessels. A normal young adult body has up to 500-600 lymph nodes, of which 60 to 70 are found in the head & neck, 100 in thorax & as many as 250 in the abdomen & pelvis. Lymph nodes are particularly numerous in the neck, abdomen & the groin.

Lymph is a clear colorless fluid which circulates in the lymphatic system. The composition of lymph fluid changes at different areas in the body. When it enters the lymph nodes lymphocytes & monocytes enter it. At the gastrointestinal tract lymph has a milk consistency due to the rich fat content.

Around 95% of lymph is water. It is quite similar to plasma except the oxygen & protein content is low in lymph & the fat content is high in lymph.

Lymph consists of the following components:

• Water – 95%.
• Proteins – Albumin, globulin, & fibrinogen (low amounts)
• Carbohydrates.
• Lymphocytes.
• Lipids – chylomicrons & lipoprotein
• Creatinine.
• Urea.
• Electrolytes
• Enzymes.

Each lymph node is encapsulated by a fibrous capsule which contains the internal cortex & medulla. The cortex is mainly composed of clusters of B cells in the outer layers & T cells in the inner layers, & may also contain antigen-presenting dendritic cells. The cortex is absent at the hilum, where the medulla reaches the surface. The medulla has plasma cells, macrophages, & B cells as well as sinuses, which are vessel-like spaces in which the lymph flows into. Inside each sinus cavity there is a smaller nodule of lymphoid tissue which is called the germinal center. Germinal center is the site for B cell proliferation during antigen presentation. The sinuses are partially divided by the capsule which allows the lymph to flow around the nodules on their way through the node.

Lymph fluid flows into the lymph node through the afferent lymphatics & enters the subscapular sinus. Numerous radial cortical sinuses lead from the subscapular sinus to the medulla, where they coalesce as larger medullary sinuses. Through the medullary sinus lymph drains into the hilum & leave the lymph node through efferent vessels. The hilum also contains the blood supply of the lymph node.

The main role of the lymph nodes is to trigger an adaptive immune reaction by filtering microorganism & other unwanted substances like waste products, cancer cells. It cleans the lymphatic fluid & take the clean fluid back to the bloodstream.

This also makes the lymph nodes vulnerable to cancer. When cancer cells enter the lymph nodes it can get trapped in & then proliferate more inside the lymph node.

Lymph nodes are small oval-shaped structures of lymphatic tissue, 0.1–2.5 cm long, distributed broadly all over the body & connected to each other by the lymphatic vessels. A normal young adult body contains up to 500 -600 lymph nodes. Each lymph node is encapsulated by a fibrous capsule which contains the internal cortex & medulla. The cortex is mainly comprises of clusters of B cells in the outer layers & T cells in the inner layers, & may also contain antigen-presenting dendritic cells. The cortex is absent at the hilum, where the medulla reaches the surface. The medulla contains plasma cells, macrophages, & B cells as well as sinuses, which are vessel-like spaces in which the lymph flows into. The main role of the lymph nodes is to trigger an adaptive immune reaction by filtering microorganism & other unwanted substances like waste products, cancer cells. It cleans the lymphatic fluid & take the clean fluid back to the bloodstream. Lymph consists of water (95%) proteins, carbohydrates, lymphocytes, lipids, enzymes & electrolytes.

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