The occipital lymph nodes are located in the back of the head, near the occipital bone of the skull. Additionally, they are located near the trapezius, as well as near the semispinalis capitis muscle's insertion point. Much like other nodes located throughout the body, the occipital lymph nodes play an active role in the body's immune system. Each node is small, possessing a ball-like shape. They are connected by lymphatic vessels. Germs, bacteria, and other foreign substances become trapped in these nodes, where they are killed by lymphocytes, a form of white blood cell. When an infection is present, the number of lymphocytes within the node may increase, which leads to swollen glands. The occipital lymph nodes are located outside of the occipital bone, not within the skull itself. These nodes filter the lymphatic vessels running through the scalp. Eventually, once foreign cells have been destroyed, the lymph drains into the bloodstream, from which impurities are eventually filtered out into the liver.