Figure 16-2
Compartments of the leg.

The leg is divided into four compartments by deep fascial membranes and bones. (Figure 16-2) These membranes not only compartmentalize the leg, but they also serve as the site of origin for leg muscles, as well as enhance the free play of muscles. Each compartment houses muscles, their nerve and arterial supply, and venous return. The action of these muscles is focused primarily on the ankle and secondarily on the foot and toes.

The superficial venous drainage of the leg is very much like the forearm. The great saphenous vein (analogous to the cephalic vein of the upper limb), begins on the dorsum of the foot, ascends on the medial side of the leg and thigh, and empties into the femoral vein in the femoral triangle.

The lesser saphenous vein also begins on the dorsum of the foot, ascends on the lateral side of the leg and empties into the popliteal vein in the popliteal fossa.

The deep veins of the leg and thigh, named for the arteries they run with, usually are paired. This dual arrangement of veins on either side of an artery is referred to as venae comitantes, or "accompanying veins." This dual venous arrangement near arteries serves to keep the venous blood moving toward the heart and keeps venous blood warm. (Figure 16-1)