Peripheral lymph nodes are small, bean-shaped structures that are part of the body’s extensive immune system. These glands are strategically distributed, acting as filters within the lymphatic system. This network of vessels and organs helps maintain fluid balance and protects against infection by identifying and fighting off foreign invaders.
Location of Peripheral Lymph Nodes
Peripheral lymph nodes are situated close to the skin’s surface, making them palpable when enlarged. One prominent group is the cervical lymph nodes, found in the neck, including areas around the jaw and at the base of the skull. These nodes often respond to infections affecting the head and neck.
The axillary lymph nodes are another cluster, located in the armpits. These nodes filter lymph fluid from the arms, chest wall, and breast tissue. In the groin, the inguinal lymph nodes collect lymph from the legs, feet, and lower abdomen.
Additional groups include the supraclavicular nodes, found just above the collarbone, and the popliteal nodes, located behind the knee. While many lymph nodes are deep within the body, these peripheral groups are accessible and often serve as indicators of immune activity.
Function Within the Immune System
Lymph nodes function as specialized filters for lymph fluid, a clear liquid containing white blood cells, proteins, and waste products. Lymph enters the nodes through afferent lymphatic vessels, flowing through a network of sinuses within the node.
Within the lymph nodes, various immune cells, particularly lymphocytes like B cells and T cells, are highly concentrated. These cells constantly monitor the filtered lymph for pathogens such as bacteria, viruses, or abnormal cells like those associated with cancer. When a foreign substance is detected, these immune cells become activated, initiating a targeted immune response.
The lymph node is where immune cells are educated, multiply, and coordinate their attack against detected threats. After activation, the fluid and activated cells exit the node through efferent lymphatic vessels, returning to circulation to address the threat.
Common Causes of Swelling
Swelling of lymph nodes, medically termed lymphadenopathy, indicates the immune system is actively responding to a threat. The most frequent cause is infection, often from common viral or bacterial sources. For example, an upper respiratory infection like the common cold or strep throat can cause neck lymph nodes to swell.
Skin infections or conditions affecting the limbs might lead to swelling in the axillary or inguinal nodes. Other infections, such as mononucleosis or HIV, can cause more widespread lymph node enlargement across multiple body regions.
Less commonly, swollen lymph nodes can arise from autoimmune disorders, where the immune system mistakenly attacks healthy tissues. Conditions like lupus or rheumatoid arthritis may present with generalized lymphadenopathy. Certain medications can also induce lymph node swelling as a side effect. In rare instances, persistent or unexplained lymph node enlargement can be a sign of cancer, including lymphomas or other cancers that have spread to the nodes.
When to Consult a Doctor
While swollen lymph nodes are often a temporary response to a common infection, certain characteristics warrant medical evaluation. Consult a healthcare provider if a swollen lymph node has no clear cause or persists for more than two to four weeks. Swelling that continues to grow or reaches a diameter of approximately one inch or more should also be assessed.
Nodes that feel hard, rubbery, or are fixed in place and do not move easily when touched are concerning signs. Medical attention is recommended if swollen lymph nodes are accompanied by unexplained weight loss, persistent fever, or night sweats. These symptoms can help a doctor determine if further investigation is necessary.