Veins are vessels that carry de-oxygenated 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 specifically the large vein in the upper arm, running from the hand to the shoulder, along the outer edge of the biceps muscle. It passes between the deltoid and pectoralis major muscles, known as the deltopectoral groove, through the deltopectoral triangle and empties into the axillary vein. The large size of the vein, its visibility through the skin, and its reasonably consistent location in the deltopectoral groove makes it generally easy to insert large cannulae. Cannulae are used to drain fluid or to administer intravenous drugs. For this reason it is sometimes known as The Houseman's Friend. However, although the cephalic vein in the forearm is often used for intravenous catheters, its close proximity to the radial nerve sometimes causes it to be damaged when the vein is cannulated.
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In Depth: Cephalic vein