Anatomy of the Leg and Foot: General Organizational Principles
 
  1. The arterial blood supply to the leg and foot is almost entirely derived from branches of the popliteal artery. Very schematically, the major arterial branches in the leg and foot are as follows:
  1. Two sets of veins drain the leg and foot: 1) Deep veins, which are usually venae comitantes accompanying the arteries of the leg and foot; and 2) Superficial veins, which drain into the great saphenous or the small saphenous vein. The two sets of veins are connected by valved perforating veins, 80 that (ideally) blood flows from superficial to deep veins and moves toward the heart mainly in deep veins. (See Fig. 18, p. 495 in Snell, Clinical Anatomy for Medical Students.)
  2. The lymphatic drainage of the leg and foot is to popliteal nodes, the vertical group of superficial inguinal nodes, and deep inguinal nodes. Popliteal nodes receive superficial lymph vessels from the lateral side of the leg and foot (the area drained by the small saphenous vein) and from deep lymph vessels accompanying the anterior and posterior tibial arteries. The efferent vessels from the popliteal nodes drain into deep inguinal nodes. The vertical group of superficial inguinal nodes receives superficial lymph vessels from the territory drained by the great saphenous vein. Efferent vessels from this group of superficial inguinal nodes drain into deep inguinal nodes. The deep inguinal nodes receive lymph from deep vessels in the lower limb that travel alongside of arteries, from the superficial inguinal nodes (horizontal and vertical groups), and from the popliteal nodes. Efferent vessels from the deep inguinal nodes drain into external iliac nodes. (See Fig. 2S, p. 513, Snell, Clinical Anatomy for Medical Students.)
  3. Autonomic innervation of the leg and foot is limited to postganglionic sympathetic nerves supplying vascular smooth muscle (vasoconstriction) and sweat glands.
  4. Somatic sensory end motor innervation of the leg and foot is almost entirely by way of branches of the sciatic nerve. Exception: The cutaneous innervation of the anteromedial portion of the leg is by way of the saphenous nerve, a branch of the femoral nerve. The major branches of the sciatic nerve are summarized schematically below. (See Figs. 8 and 9, pages 481 and 482, Snell, Clinical Anatomy for Medical Students for a diagram summarizing the distribution of the major cutaneous nerves of the lower limb. Study suggestion: Color code these figures to indicate which areas of the lower limb receive cutaneous innervation from branches of the following nerves: obturator, femoral, common peroneal, deep peroneal, superficial peroneal, tibial. The sources of motor innervation to muscles of the leg and foot should be evident if you understand Principle 6, below.)
 
  1. The leg is subdivided by the arrangement of bones, interosseous membrane, and fascial septa into 3 fascia] compartments. Each of these has its own muscles, its own nerve supply, its own "gateway" to the foot, and (by and large) its own blood supply. The figure below is a highly schematic diagram (a cross-section through the leg) summarizing the compartmental organization of the leg.