Lymph node

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Lymph node
Schematic of lymph node showing lymph sinuses.svg
Schematic diagram of lymph node showing the flow of lymph through the lymph sinuses. Note: Outflowing lymph has more lymphocytes
SystemLymphatic system
  (Redirected from Lymph gland)
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Lymph node
Schematic of lymph node showing lymph sinuses.svg
SystemLymphatic system


Lymph nodes also have clinical significance. They become inflamed or enlarged in various infections and diseases which may range from trivial, such as a throat infection, to life-threatening such as cancers. In the latter, the condition of lymph nodes is so significant that it is used for cancer staging, which decides the treatment to be employed, and for determining the prognosis. When swollen, inflamed or enlarged, lymph nodes can be hard, firm or tender.[1]

Lymph nodes are not part of the body's system for handling illnesses stemming, for example, from environmental toxicity or personal injury—those tasks are handled by the liver and kidneys in the former and the muscular-skeletal system in the latter. The lymphatic system is structured to address biological infection by other organisms as well as biological breakdowns/ errors within the same body (i.e., cancer). "Illness" and "disease" may be caused by any number of events including biological, chemical, physical, and psychological sources among others. A response to illness that includes inflammation of the lymph nodes specifically indicates a biological factor.

Lymph nodes can also be diagnosed by biopsy whenever they are inflamed. Certain diseases affect lymph nodes with characteristic consistency and location.


The lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae. The substance of the lymph node is divided into the outer cortex and the inner medulla surrounded by the cortex all around except at the hilum, where the medulla comes in direct contact with the surface.[2]

Thin reticular fibers, elastin and reticular fibers form a supporting meshwork called reticular network (RN) inside the node, within which the white blood cells (WBCs), the most prominent ones being lymphocytes, are tightly packed as follicles in the cortex. Elsewhere, there are only occasional WBCs. The RN not only provides the structural support, but also the surface for adhesion of the dendritic cells, macrophages and lymphocytes. It allows exchange of material with blood through the high endothelial venules and provides the growth and regulatory factors necessary for activation and maturation of immune cells.[3]


A lymph sinus is a channel within the lymph node lined by the endothelial cells along with fibroblastic reticular cells and allows smooth flow of lymph through them. Thus, the subcapsular sinus is a sinus immediately deep to the capsule, and its endothelium is continuous with that of the afferent lymph vessel. It is also continuous with similar sinuses flanking the trabeculae and within the cortex (cortical sinuses). The cortical sinuses and that flanking the trabeculae drain into the medullary sinuses, from where the lymph flows into the efferent lymph vessel.[2]

Multiple afferent lymph vessels that branch and network extensively within the capsule bring lymph into the lymph node. This lymph enters the subcapsular sinus. The innermost lining of the afferent lymph vessels is continuous with the cells lining the lymph sinuses.[2] The lymph gets slowly filtered through the substance of the lymph node and ultimately reaches the medulla. In its course it encounters the lymphocytes and may lead to their activation as a part of adaptive immune response.

The concave side of the lymph node is called the hilum. The efferent attaches to the hilum by a relatively dense reticulum present there, and carries the lymph out of the lymph node.


The cortex of the lymph node is the peripheral portion underneath the capsule.[4] In the cortex, the subcapsular sinus drains to trabecular sinuses, and then the lymph flows into the medullary sinuses.



There are two named structures in the medulla:

The medulla contains large blood vessels, sinuses and medullary cords that contain plasma cells secreting antibody.

Shape and size[edit]

Human lymph nodes are bean-shaped and range in size from a few millimeters to about 1–2 cm long.[2] They may become enlarged due to a tumor or infection, or inflamed due to leukemia. Lymphocytes, types of white blood cells, are located within honeycomb structures of the lymph nodes. Lymph nodes are enlarged when the body is infected, primarily because there is an elevated rate of trafficking of lymphocytes into the node from the blood, exceeding the rate of outflow from the node, and secondarily as a result of the activation and proliferation of antigen-specific T and B cells (clonal expansion). In some cases, they may feel enlarged because of a previous infection; although one may be healthy, one may still feel them residually enlarged.






Clinical significance[edit]

Micrograph of a mesenteric lymph node with colo rectal adenocarcinoma, the most common type of colorectal cancer.


Lymphodoema is a fairly widespread condition of the lymphatic system resulting in localised fluid retention and tissue swelling. Affected tissues are at risk of infection. Primary lymphodoema generally results from poorly developed or missing lymph nodes. Secondary lymphodoema results mostly from the dissection of lymph nodes during breast cancer surgery and also from other treatments usually involving radiation.

See also[edit]

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