Surgical Anatomy of the Thymus Gland

Abstract

The thymus is an H-shaped, bilobed gland that sits largely in the anterior mediastinum but extends also into the lower neck. In infancy through adolescence the gland it quite large, filling the entire anterior mediastinum and even bulging the pleurae out laterally into each hemithorax. With increasing age, as its role in maturation of the immune system diminishes, the thymus shrinks dramatically. By age 50, the normal thymus is a diminutive, mostly fatty structure.