Lung

**Semantic type:** Body Part, Organ, or Organ Component

**Definition:** One of a pair of viscera occupying the pulmonary cavities of the thorax, the organs of respiration in which aeration of the blood takes place. As a rule, the right lung is slightly larger than the left and is divided into three lobes (an upper, a middle, and a lower or basal), while the left has two lobes (an upper and a lower or basal). Each lung is irregularly conical in shape, presenting a blunt upper extremity (the apex), a concave base following the curve of the diaphragm, an outer convex surface (costal surface), an inner or mediastinal surface (mediastinal surface), a thin and sharp anterior border, and a thick and rounded posterior border.

**Synonyms:** - LUNG - Lung structure (body structure) - Lung, NOS - Lungs - Respiratory System, Lung - lung - lung - pulmo