Borders of the lung

The anterior border of the lung is thin and sharp, and overlaps the front of the pericardium.

The anterior border of the right lung is almost vertical, and projects into the costomediastinal sinus; that of the left lung presents, below, an angular notch, the cardiac notch, in which the pericardium is exposed.

Opposite this notch the anterior margin of the left lung is situated some little distance lateral to the line of reflection of the corresponding part of the pleura.

The posterior border of the lung is broad and rounded, and is received into the deep concavity on either side of the vertebral column.

It is much longer than the anterior border, and projects, below, into the phrenicocostal sinus.

The inferior border of the lung is thin and sharp where it separates the base from the costal surface and extends into the phrenicocostal sinus; medially where it divides the base from the mediastinal surface it is blunt and rounded.