Median Cubital Vein
The structure indicated is the median cubital vein.
The median cubital vein is a superficial vein located in the cubital fossa anteriorly in the elbow, and connects the basilic and cephalic veins. The basilic and cephalic veins are two large superficial veins of the upper limb which arise from the dorsal venous network of the hand.
The basilic vein arises medially from the dorsal venous network of the hand, whereas the cephalic vein arises laterally from the dorsal venous network. These two veins drain to the axillary vein.
The deep venous system of the upper limb follows the arteries, and consists of the radial, ulnar and brachial veins.