Lymph fluid normally flows through a network of lymph vessels. These lymph vessels connect to a group of lymph nodes. The nodes act as a filter. They trap or destroy anything harmful that the body does not need. Show
Inside the lymph nodes are white blood cells, also called lymphocytes. These white blood cells attack and break down bacteria, viruses, damaged cells or cancer cells. The lymph fluid carries the waste products and destroyed bacteria back into the bloodstream. The liver or kidneys then remove these from the blood. The body passes them out with other body waste, through bowel movements (poo) or urine (pee). Lymph nodes sometimes trap bacteria or viruses that they cannot destroy straight away. For example, they may do this when you have an infection. When the lymph nodes are fighting the infection, they often swell and become sore to touch. Sometimes cancer cells spread from where a cancer started (the primary site) to other parts of the body. They can travel around the body in the blood or through lymph fluid. When these cancer cells reach another part of the body, they may grow and form another tumour. This is called a secondary cancer or a metastasis. Cancer cells can sometimes spread into the lymph nodes from a cancer somewhere else in the body. This is called secondary cancer in the lymph nodes. Cancer can also start in the lymph nodes themselves. This is called lymphoma. If there is cancer in the lymph nodes, they may swell, but are usually painless. There are different causes of swollen lymph nodes. But if you notice a painless, swollen lymph node, it is important to get it checked by your GP. The lymph system is a network of organs, lymph nodes, lymph ducts, and lymph vessels that make and move lymph from tissues to the bloodstream. The lymph system is a major part of the body's immune system. Lymph is a clear-to-white fluid made of:
Lymph nodes are soft, small, round- or bean-shaped structures. They usually cannot be seen or easily felt. They are located in clusters in various parts of the body, such as the:
Lymph nodes make immune cells that help the body fight infection. They also filter the lymph fluid and remove foreign material such as bacteria and cancer cells. When bacteria are recognized in the lymph fluid, the lymph nodes make more infection-fighting white blood cells. This causes the nodes to swell. The swollen nodes are sometimes felt in the neck, under the arms, and groin. The lymph system includes the:
Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW. Lymphatic system. In: Ball JW, Dains JE, Flynn JA, Solomon BS, Stewart RW, eds. Seidel's Guide to Physical Examination. 9th ed. Philadelphia, PA: Elsevier; 2019:chap 10. Hall JE, Hall ME. The microcirculation and lymphatic system: capillary fluid exchange, interstitial fluid, and lymph flow. In: Hall JE, Hall ME eds. Guyton and Hall Textbook of Medical Physiology. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 16. Updated by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Lymph nodes, sometimes referred to as lymph glands, are an important part of the immune system. Lymph nodes are clustered throughout the body and function as filters, removing foreign particles from fluids that run through the vessels of the lymphatic system. Within lymph nodes are white blood cells called lymphocytes that help neutralize foreign agents like bacteria. Swollen lymph nodes are a sign that the body is fighting infection, and they may be tender and painful. In some cases, swollen lymph nodes may be a sign of cancer. This article describes lymph node structure and function, and the types of lymph nodes found throughout the body. It lists some conditions that can affect them and offers information about when you should contact a healthcare provider about a swollen lymph node. dardespot / Getty Images Lymph nodes are small, bean-shaped organs that are part of the lymphatic system. The lymphatic system is a network of vessels and organs that isolate and neutralize foreign agents and particles that can do the body harm. In addition to lymph nodes, lymphatic fluid, and lymphatic vessels, the system is comprised of the thymus gland, tonsils, spleen, and bone marrow. Lymph nodes vary in size from a few millimeters to up to 2 centimeters in diameter. There are hundreds located throughout the body, but they are mainly clustered in certain parts of the body. Lymph Node FunctionLymph nodes work to identify and filter out foreign agents that cause infections. To do this, lymph nodes contain two different types of white blood cells:
When a foreign agent has been trapped and the immune defenses are activated, the body will respond with inflammation. This causes the lymph nodes to swell. Swollen lymph nodes, referred to as lymphadenopathy, can often be felt and seen, but not always. Some may be painful; others are not. Not every particle that is filtered by the lymph nodes can be neutralized. One example is cancer cells that are shed from a nearby tumor. Even though lymph nodes cannot kill the cancer cells, they may be able to isolate and contain them during the early stages of the disease. When to See a Healthcare ProviderLymph nodes may remain swollen for up to two weeks. If they don't get better or keep getting bigger, contact your healthcare provider. Click Play to Learn More About Lymph NodesTypes and LocationsLymph nodes are clustered throughout the body in key locations. These include the armpits, neck, groin, upper abdomen, and mediastinum (the area between the lungs that contains all the principal organs of the chest). Swollen lymph nodes in the armpits, neck, and groin can often be felt. Those in the mediastinum and upper abdomen may only be revealed with imaging tests such as a computed tomography (CT) scan or ultrasound. The types and locations of lymph nodes vary as follows: Cervical Lymph NodesCervical lymph nodes are those in the neck. They are further broken down by their location:
Axillary Lymph NodesAxillary lymph nodes are the lymph nodes located in the armpit (axilla). There are usually between 10 and 40 lymph nodes in the axilla. The axillary lymph nodes are important in the diagnosis of breast cancer. When cancer cells are shed from a breast tumor, they first travel to the axillary nodes. Because cancer cells tend to spread through lymph nodes in a specific pattern, doctors can often tell how advanced the cancer is. Supraclavicular Lymph NodesSupraclavicular lymph nodes are located just above the collarbone (clavicle). Most of the time, the enlargement of supraclavicular lymph nodes is a sign of a serious disease such as lung cancer or lymphoma (a type of blood cancer). Mediastinal Lymph NodesMediastinal lymph nodes reside in the center of the chest cavity between the lungs. People cannot feel mediastinal lymph nodes, but they can be seen in imaging studies such as a CT scan or positron emission tomography (PET) scan. Checking mediastinal lymph nodes is essential to the staging of lung cancer and some lymphomas. Inguinal Lymph NodesInguinal lymph nodes are located in the groin. Because they are responsible for filtering lymphatic fluids from the feet to the groin, they can become swollen for many reasons. These include injuries, sexually transmitted diseases, skin infections, yeast infections, and cancer. Retroperitoneal Lymph NodesRetroperitoneal lymph nodes are situated at the back of the abdomen behind the tissues that cover the abdominal wall. These are the nodes to which testicular cancer first spreads. They can only be seen in imaging studies. Mesenteric Lymph NodesMesenteric lymph nodes lie deep within the abdomen in the membranes that surround the intestine. These nodes often become swollen due to gastroenteritis (stomach flu) but are also sometimes affected by inflammatory bowel disease (IBD) and lymphoma. Pelvic Lymph NodesPelvic lymph nodes are situated in the lower abdomen in the area that contains the hip bones, bladder, rectum, and reproductive organs. Pelvic lymph nodes are only seen in imaging studies. Swollen pelvic lymph nodes may be a sign of bladder, prostate, cervical, ovarian, or anal cancer. Where Lymph Nodes Are LocatedLymph nodes are classified by their location, including:
Associated ConditionsThere are many conditions that can directly or indirectly affect the lymph nodes. Some are relatively mild and treatable, while others are more serious. LymphadenopathyLymphadenopathy, or the swelling of lymph nodes, is not a disease but a symptom of a disease. Based on its location and features, lymphadenopathy can reveal a lot about what is going on inside the body. The features of lymphadenopathy may be described as:
Verywell / Brianna Gilmartin Lymphadenitis/LymphangitisLymph nodes can "catch" viruses and bacteria but are also susceptible to infections themselves.
One such example is a bacterial infection from cats called cat scratch fever. The disease can cause swollen lymph nodes that last for months as well as fever, muscle aches, and nausea. CancerLymph nodes are commonly involved with cancer, but their role differs based on whether a solid tumor or lymphoma is involved. With solid tumors such as breast cancer, cancer cells usually travel to nearby lymph nodes before metastasizing (spreading to other parts of the body). Solid tumor cancers are typically staged based on the TNM system. The TNM system describes the severity of the disease based on the size of the tumor (T), the number and location of lymph nodes with cancer (N), and the presence or absence of metastasis (M). With lymphoma, cancer starts in the lymph nodes. When lymphomas spread to other parts of the body, it is not referred to as metastasis but rather as "extranodal involvement." Lymphoma is staged based on the number and location of affected lymph nodes, whether one or both sides of the body are involved, and if there is extranodal involvement. Conditions Affecting Lymph NodesConditions that directly or indirectly affect the lymph nodes include:
SummaryLymph nodes are small, bean-shaped organs that support the immune system by trapping foreign agents and killing them. They do so by filtering bacteria, viruses, and other disease-causing agents circulating in the lymphatic system. White blood cells, called lymphocytes, are then recruited to control infection. Lymph nodes are clustered throughout the body, including the neck (cervical lymph nodes), groin (inguinal lymph nodes), and armpits (axillary lymph nodes). There are internal lymph nodes in the abdomen (mesenteric and retroperitoneal), chest cavity (mediastinal), and lower abdomen (pelvic). Swollen lymph nodes
(lymphadenopathy) can occur in response to an infection or disease in any part of the body. When a lymph node is infected and becomes swollen, it is referred to as lymphadenitis. Cancer can also affect lymph nodes either as it spreads from a tumor or starts in the lymph nodes themselves (lymphoma). Frequently Asked Questions
What body system is the lymph nodes in?Lymph nodes (or lymph glands) are small lumps of tissue that contain white blood cells, which fight infection. They are part of the body's immune system and filter lymph fluid, which is composed of fluid and waste products from body tissues.
Is lymph part of the circulatory system?The lymphatic system is a subsystem of the circulatory system in the vertebrate body that consists of a complex network of vessels, tissues, and organs. It helps maintain fluid balance in the body by collecting excess fluid and particulate matter from tissues and depositing them in the bloodstream.
Is the lymph nodes part of the nervous system?However, in 2015, scientists found convincing evidence that lymphatic pathways exist within the central nervous system. This article will review the role of the lymphatic pathway, previous dogma associated with central nervous system lymphatic tracts and the new discovery of lymphatic vessels in the brain.
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