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 cardiac notch lies along the fifth and sixth intercostal space, and the spaces can be used to access the heart in pericardiocentesis to relieve cardiac tamponade.
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This article incorporates text from a public domain edition of Gray's Anatomy.