Veins are blood vessels that carry oxygen-depleted blood from the capillaries back to the heart. In human anatomy, blood flows from a variety of smaller veins, draining into the cephalic vein. This is the large vein in the upper arm that runs from the hand to the shoulder, along the outer edge of the biceps muscle. It passes between the deltoid and pectoralis major muscles, via the ‘deltopectoral groove’, through the deltopectoral triangle. It ultimately empties into the axillary vein. In most people, it is easy to insert a large cannulae into this vein. This is due to the large size of the vein, its visibility through the skin, and its reasonably consistent location in the deltopectoral groove. Cannulae are flexible tubes used to drain fluid. They may also be used to administer intravenous drugs. The cephalic is one of the most commonly used veins for intravenous catheters. However, its close proximity to the radial nerve sometimes causes it to be damaged when the vein is cannulated.