The Great Saphenous Vein is the longest vein in the human body, running along the length of the leg. It starts at the foot and travels up the inner side of the leg and thigh, eventually draining into the femoral vein near the groin. This vein plays a crucial role in returning blood from the lower extremities back to the heart. This vein is often used in medical procedures, such as bypass surgery, due to its accessibility and size. Conditions like varicose veins can affect the Great Saphenous Vein, leading to swelling and discomfort. Proper functioning of this vein is essential for healthy circulation.