The cephalic vein is one of two main superficial veins in the human arm that extend from the wrist to the shoulder. At the top of the arm near the shoulder, the cephalic vein slides through a groove between the deltoid and pectoralis major muscles. A superficial vein is one that is located close to the surface of the skin. The depth of the cephalic vein varies from person to person. On many people, superficial veins are visible to the eye as a bluish-gray line.
Veins carry deoxygenated blood back to the heart after the exchange of carbon dioxide and oxygen — they are rich with waste and low in oxygen. The blood itself is actually a dark shade of red that is almost maroon. Since the skin refracts light, the vein appears to be a bluish gray. There are valves in the vein that operate like the gates or locks on a canal. They resist the pull of gravity and ensure that the blood always goes in the same direction — flowing back toward the heart.
There are several veins in the arms that form a network with the capillaries to drain the blood back to the heart. The other main superficial vein, the basilic vein, runs parallel to the cephalic vein. Another vein called the median cubital vein forms a connection between the two.
The veins in the arm are the most common places used for extracting blood samples. When a tourniquet is applied to the arm to slow the flow of blood, the vein distends or expands and usually becomes more visible. The cephalic vein is often used in hospital settings to introduce fluids intravenously (IV). Blood samples are usually taken from the median cubital vein.
While the blood in the veins is flowing back toward the heart, the blood in the arteries is moving away from the heart. Ordinarily, they do not intersect. For some people who have severe kidney disease, an artificial connection is made between the cephalic vein and a nearby artery to make the dialysis process easier.
Origins of the word "cephalic" reveal a mixed meaning. The word cephalic comes from the Arabic stem al-kifal, meaning outer, which refers to its position on the arm. In Latin, cephalicus refers to something to do with the head. When the word was translated into Medieval Latin, it was mistakenly translated using the Latin word cephalic.
