Once blood is oxygenated in the lungs, it returns to the heart where it is pumped throughout the body. A web of blood vessels—arteries, veins, and capillaries—circulate blood to organs, muscles, and bones.

Oxygenated blood leaves the heart through the large, hollow vessel known as the thoracic aorta, which becomes the abdominal aorta. Just below the kidneys, it splits into two main branches near the abdomen. These are known as the common iliac arteries. One travels down each leg and branches into internal and external iliac arteries, which supply blood to other branches, including the femoral artery.

The femoral artery, the major artery in the thigh, continues to branch into other arteries as blood travels all the way down to the tips of the toes.

Other important arteries of the leg include:

• Popliteal artery: A branch of the femoral artery, the popliteal artery branches further to supply blood to the knee, thigh, and calf. It ends at the anterior and posterior tibial arteries.
• Posterior tibial artery: This branch of the popliteal artery supplies oxygenated blood to the leg and sole of the foot. It runs on the inside of the leg and is accompanied by the posterior tibial vein.
• Anterior tibial artery: The other branch of the popliteal artery from the back of the knee, it supplies blood to the muscles of the leg and foot. 
• Peroneal artery: This is the largest branch of the posterior tibial artery. It supplies blood to the outside and back of the ankle and calf muscles. It ends at the lateral calcaneal artery.
• Plantar arteries: The plantar arteries—lateral, medial, and deep—form a looping web across the foot and down through each toe and unite with the dorsalis pedis artery.
• Dorsalis pedis artery: This artery supplies blood to the surface of the foot as a continuation of the anterior tibial artery. The dorsalis pedis vein accompanies this artery.

With an opposite function to arteries, veins return blood to the heart, where it will begin its journey all over again. Often, veins run the same course as arteries, as with the dorsalis pedis artery and vein. Important veins of the leg include the internal and external iliac veins, femoral vein, saphenous vein, popliteal vein, tibial vein, and the venous arch of the foot.

Nerves in the leg send messages to the brain, including indications of heat, pain, and movement. The major nerve of the leg is the sciatic nerve. It begins in the lower back and runs down to the lower leg. Other large nerves in the leg include the tibial nerve, medial cutaneous nerve, and deep peroneal nerve.