Neurovasculature of the lower limb
The structures of the lower limb are mainly supplied with arterial blood by the femoral artery, which is a continuation of the external iliac, a terminal branch arising from the abdominal aorta. The external iliac artery becomes the femoral artery as it runs underneath the inguinal ligament, and enters the femoral triangle.
In the femoral triangle, the posterolateral aspect of the femoral artery gives off a deep branch, the profunda femoris artery. This artery travels posteriorly and distally to divide into three main branches: perforating branches, lateral femoral circumflex artery, and the medial femoral circumflex artery. These arteries supply the thigh region along with the obturator and inferior gluteal artery.
After exiting the femoral triangle, the femoral artery continues to the posterior compartment of the thigh, where it becomes known as the popliteal artery. The popliteal artery gives off genicular branches that supply the knee joint, and then continues through the popliteal fossa. At the lower border of the popliteus muscle, it terminates into anterior and posterior tibial arteries. The posterior tibial artery descends and gives off the fibular artery. All these blood vessels supply the region of the leg.
The anterior tibial artery runs inferiorly down the leg and into the foot to become the dorsalis pedis artery. The dorsalis pedis and the posterior tibial artery form the main vascular supply of the foot. The posterior tibial artery splits into lateral and medial plantar arteries upon entering the sole of the foot.
The lower limb veins drain deoxygenated blood back to the heart. They are divided into superficial and deep veins. The superficial veins are located in the subcutaneous tissue, while deep veins occur beneath the deep fascia of the lower limb, accompanying major arteries and bearing their names. Both types of veins have valves, but they are more numerous within the deep veins.
The two major superficial veins in the lower limb are the great and small saphenous veins. The great saphenous vein is formed by the union of the dorsal venous arch of the foot with the dorsal vein of the great toe. Immediately inferior to the inguinal ligament, the great saphenous vein empties into the femoral vein. The small saphenous vein arises on the lateral side of the foot. It is formed by the union of the dorsal venous arch with the dorsal vein of the little toe, and empties into the popliteal vein.
Deep veins occur in pairs and are contained within a vascular sheath with the arteries they accompany. Perforating veins from the dorsal venous arch penetrate the deep fascia and supply the anterior tibial vein, while the medial and lateral plantar veins form the posterior tibial and fibular veins. All deep veins flow into the popliteal vein and then drain into the femoral vein, which passes deep to the inguinal ligament to become the external iliac vein.
In the thigh region, the femoral nerve innervates the muscles of the anterior compartment. It is the largest nerve of the lumbar plexus. The obturator nerve is a branch of the lumbar plexus that supplies the adductor group of muscles in the medial compartment of the thigh. The sciatic nerve is the longest and widest nerve in the human body. It innervates the posterior muscle compartment of the thigh, and gives off its larger tibial branch that supplies the muscles of the popliteal fossa.
The common peroneal nerve is derived from the sciatic nerve as well. It divides into superficial and deep fibular branches. The superficial fibular branch supplies the lateral compartment of the leg, while the deep fibular branch supplies the anterior muscle compartment of the leg, as well as the dorsum part of the foot. The posterior compartment is innervated by the posterior tibial nerve, which is a continuation of the tibial nerve. The tibial nerve terminates into medial and lateral plantar nerves, which are responsible for the innervation of most of the muscles in the foot.