Which surface of the lung faces the sternum, costal cartilage, and ribs?

The costal surface of the lung is the area that is in direct contact with the ribs, costal cartilage, and the sternum. This surface is named for its anatomical relationship to the thoracic cavity, where it faces the chest wall. It is smooth and concave to accommodate the shape of the thorax and plays an essential role in the respiratory mechanics as the lungs expand and contract during breathing.

The other surfaces of the lung serve different anatomical functions: the mediastinal surface faces the heart and other structures in the mediastinum, the diaphragm surface is oriented towards the diaphragm, and the superior surface faces upwards towards the apex of the lung beneath the collarbone. Each surface has distinct anatomical relationships and is named based on what structures they are adjacent to, but when specifically addressing which lung surface is oriented toward the sternum, costal cartilage, and ribs, the costal surface is the correct designation.