Great Saphenous Vein
The structure indicated is the great saphenous vein
The great saphenous vein is a large superficial vein (the longest vein in the human body), which begins from the medial aspect of the dorsal venous arch
of the foot. It then passes anteriorly, in front of the medial malleolus
and ascends medially up the lower limb to drain into the femoral vein
in the femoral triangle
Learn about the femoral triangle
in this anatomy tutorial.
Learn about the veins of the body
in this tutorial.