Final answer:
The great saphenous vein drains into the femoral vein, which becomes the external iliac vein as it crosses the body wall.
Step-by-step explanation:
Blood in the great saphenous vein will flow next into the femoral vein. The great saphenous vein is a large, subcutaneous, superficial vein of the leg and is the longest vein in the human body. It is responsible for draining the superficial portions of the leg and thigh. When the great saphenous vein approaches the groin area, it empties into the femoral vein, which is a deeper vein. The femoral vein also receives blood from the deep femoral vein and the femoral circumflex vein. The femoral vein, after receiving the blood from the great saphenous vein, progresses upwards toward the lower part of the abdomen where it crosses the body wall and becomes known as the external iliac vein.