Lymph nodes are small, bean-shaped structures that are part of the body's lymphatic system and immune system. They function as filters for lymph fluid, which is a clear fluid that circulates throughout the body, carrying waste products, bacteria, viruses, and other foreign substances. Lymph nodes contain immune cells called lymphocytes (including B cells and T cells) that help detect and fight infections, cancer cells, and other harmful invaders

. There are hundreds of lymph nodes distributed throughout the body, commonly found in clusters in areas such as the neck, armpits, groin, chest, and abdomen. Lymph fluid travels through lymphatic vessels into the lymph nodes, where the immune cells filter out and destroy germs, damaged cells, and abnormal cells before the fluid returns to the bloodstream

. Structurally, each lymph node is enclosed in a fibrous capsule and consists of an outer cortex and an inner medulla. The nodes serve as sites where lymphocytes multiply and mount immune responses by producing antibodies and activating T cells against antigens presented by other immune cells

. In summary, lymph nodes are essential components of the immune system that filter lymph fluid, trap harmful substances, and coordinate immune responses to protect the body from infection and disease