Definition for Apex
From Biology Forums Dictionary
In anatomy, the apex of the lung is the rounded upper part of the human lung. It extends into the root of the neck, reaching between 2.5 cm and 4 cm above the level of the sternal end of the first rib. A sulcus, produced by the subclavian artery as it curves in front of the pleura, runs upward and lateralward immediately below the apex.