This figure is a simplified diagram of the human lymphatic system. It comprises a network of vessels which terminate in beds of tiny lymphatic capillaries; these are shown in detail in a blow-up diagram of the lymphatic system within the thumb. At locations along the lymph vessels are small oval-shaped structures called lymph nodes. These are distributed widely throughout the body and are clustered in the groin, under the arm and in the abdomen, in association with the gut. Other lymphoid structures present and their locations are the tonsils (at the back of the soft palate), the thymus (in the chest) and the spleen (in the upper left of the abdomen). There is also lymphoid tissue in the soft interior of the bones, called the bone marrow.