The lingual tonsils (tonsilla lingualis) are a pair of oval-shaped organs located at the back of the tongue behind the foramen cecum and the sulcus terminalis in the mucous membrane covering the tongue. They enlarge gradually from birth to about seven years of age and then shrinks. Each oval consists of a large number of lymphoid follicles. The lingual tonsils are part of the lymphatic system and are important to the body's defense against infection. They are composed of lymphoid tissue, which contains germ-killing cells. The tonsils help protect against upper respiratory tract infection.