The Anatomy of the Median Cubital Vein

There are a lot of blood vessels in the body. In fact, if you lined up all the arteries, veins, and capillaries, they would stretch for almost 100,000 miles. It can be tricky to distinguish one vessel from the next—especially with the naked eye—but some parts of the vascular system stand out more than others. The median cubital vein is one of them.

The median cubital vein, also known as the median basilic vein, is located in the triangular area inside the elbow known as the cubital fossa. It is a superficial vein, meaning that it lies close to the skin, making it a preferred site for drawing blood and establishing intravenous access.

Anatomy

The median cubital vein is a part of the circulatory system. Arteries, veins, and capillaries work together to carry blood, oxygen, nutrients, and waste products throughout the body. Arteries carry oxygen-rich blood to tissues, while veins carry blood that is depleted of oxygen and nutrients back to the heart and lungs to be replenished with more oxygen. Capillaries join the two together.

The median cubital vein is the most prominent superficial vein in the body, and can easily be seen in most people at the inner fold of the elbow. It connects the basilic and cephalic veins, the two primary veins of the upper limb that carry blood from the hand, forearm, and arm back to the heart.

Structure

Like most veins, the median cubital vein is made up of several layers of membranes, muscles, and connective tissues, including:

• An inner lumen, or opening, ranging from 2.3 to 4.9 millimeters (mm)
• Valves that help push blood back to the pulmonary system
• Endothelium, the cells lining the interior surface of blood vessels
• Basement membrane, an extracellular matrix of proteins that forms a barrier between tissues
• Smooth muscle, muscle providing pressure to blood vessels and organs
• Adventitia, the outermost layer of a blood vessel’s wall

These layers work together to push deoxygenated blood from tissues all over the body back to the lungs. In the lungs, the blood is replenished with oxygen, then carried to the heart, and pumped back out to the body through arteries.

Location

The median cubital vein connects the two major superficial veins in each arm:

• The basilic vein begins in the outer part of the hand near the pinky finger, extending up into the axilla, or armpit.
• The cephalic vein begins at the inner part of the hand near the thumb, and extends upward to the outer top of the shoulder.

Both of these vessels eventually empty into the axillary vein.

The median cubital vein runs upward diagonally from the cephalic to the basilic vein at the inner part of the elbow. It lies about 2–3 mm below the surface of the skin.

Anatomical Variations

The median cubital vein variably forms as either an H- or M-shaped pattern. While an upward diagonal configuration of the median cubital vein between the basilic and cephalic veins is considered standard, one study claims only about half of adults have this configuration. In other people, the basilic or cephalic vein may run in a different pattern, sometimes eliminating the connecting median cephalic vein altogether.

While cases of an absent median cephalic vein are rare, it is sometimes seen in both men and women. There also have been cases where people have two median cubital veins, but there is a lack of studies to determine how common this variation might be.

Function

The function of all veins in the arm is the same—to return deoxygenated blood back to the pulmonary system for replenishment. The basilic vein carries the most blood back to the lungs, and the median cubital vein helps facilitate drainage between the basilic and cephalic veins.

Clinical Significance

The median cubital vein is not critical to life, but it does help facilitate venous return from the arms back to the pulmonary system. The significance of this vein is its use in venipuncture, the procedure that collects blood for laboratory testing. Since it’s easy to see, the median cubital vein is routinely used for drawing blood and as a site to place an intravenous (IV) cannula. It is preferred for these purposes because it’s large and has a low tendency to move, or roll, when the needle is inserted. There are also fewer nerve endings surrounding this vein, making venipuncture less painful at this site.

The lack of nerves in close proximity also means nerves won’t be damaged when the vein is accessed. The median cubital vein also lies over arterial vessels, protecting them when the arm is outstretched and the skin of the interior elbow is taut.