The upper limb is highly mobile and well evolved. The vascular supply and venous drainage all facilitate the correct functioning of our upper limbs, and reflect the final picture of our embryological development.
The various vessels we have within our upper limbs all derive from vessels in our foetal life, adapted and transformed to fulfill their roles once we were born. The venous drainage of the upper limb is achieved via a deep and superficial system. The superficial system is what we are able to see from the surface, and comprises the basilic and cephalic veins in the forearm, connected by the median cubital vein, as well as the dorsal venous network of the hand. The deep veins mirror the arteries, and distally are found in pairs known as venae comitantes.
The venous system of the upper limb originates from the anterior cardinal veins in the embryo, which drain the cephalic half of the embryo proper. The posterior cardinal veins drain the rest of the embryo. During the fourth week, the cardinal veins form a symmetrical system. Formation of the vena cava system is defined by the appearance of several anastomoses resulting in blood being channeled to the right side, which facilitates the return of blood to the right atrium for further circulation.
The anastomosis between the anterior cardinal veins develops into the left brachiocephalic vein. The vast majority of the blood from the left side of the head and the left upper extremity is then channeled to the right. The adult venous system is much more variable than the arterial system. Through transformative processes during development, the individual sections arise from various portions of the embryonic venous system.
Drainage and Course
The basilic vein runs down the ulnar side of the arm, and also helps in draining the dorsal venous network of the hand. It is shorter than the cephalic vein, and terminates once it joins the brachial vein near the elbow. The basilic vein pierces the deep fascia at the elbow and joins the venae commitantes of the brachial vein to form the axillary vein.
The basilic vein drains into the brachial vein (part of the deep venous system), which then drains into the axillary vein once it crossed the inferior border of teres major. The axillary vein now joins the cephalic vein (part of the superficial venous system), and once this large vein crosses the lateral border of the first rib, it is renamed the subclavian (under the clavicle) vein.
The veins of this system contain valves within their lumen, which prevent backflow. They are more abundant in the veins of the deep system, although they do exist in superficial veins. They are commonly found where the veins anastomose.
When dissecting superficial fasciae, it is important to be very careful when making the first incision so as to leave the superficial veins undamaged. Commonly, the veins have thinner walls than arteries, are found more superficially, and usually are not as pale.