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Vein Anatomy

Leg Diagram Veins carry the blood to the heart. They carry dark red blood that doesn’t have much oxygen. Veins differ from arteries in their basic anatomy; they have thin walls and need valves to keep blood from pooling, whereas arteries do not have nor need valves since the blood is being pushed directly by the heart’s pumping action.

There are three categories of veins at work in our upper and lower extremities:

  • Deep veins lie within the muscle compartments surrounded by fascia (a tough white material that separates the subcutaneous fat from the muscles).  With every step, the muscles contract and squeeze the deep veins, forcing the blood upward from valve to valve.
  • Superficial veins lie outside the fascia, close to the surface of the body.  The great saphenous vein is a superficial vein which runs from the inside of the ankle up the leg and thigh to dive deep in the groin to join the femoral vein (a deep vein).  In our lower legs, the small saphenous vein is a superficial vein that runs on the outside of the ankle up towards the back of the knee where it dives deep to join the popliteal vein (a deep vein).
  • Perforator Illustration Communication veins (also known as perforator veins) connect the superficial veins to the deep veins.  These communicating veins have to cross through small holes in the fascia in order to reach the deep veins.  Each communicating vein has a valve that lets blood go from the surface into the deep vein system, but not the reverse.  When your calf muscles squeeze as you walk, the venous blood in the deep veins is forced upward toward the heart.