The saphenous vein is a blood vessel primarily located in the legs. Its location is key to understanding its function within the circulatory system and its relevance in medical contexts. This vein returns blood to the heart.
Its Path Through the Body
The saphenous venous system in each leg consists of two main superficial veins: the Great Saphenous Vein (GSV) and the Small Saphenous Vein (SSV). These veins lie close to the skin’s surface, distinguishing them from deeper veins located beneath layers of muscle and tissue. The GSV is the longest vein in the human body.
The Great Saphenous Vein originates at the top of the foot, from the medial end of the dorsal venous arch. It travels upward along the inner surface of the leg, passing in front of the medial malleolus (the bony prominence on the inside of the ankle). It continues its ascent along the medial side of the leg and thigh, terminating in the upper thigh. There, it drains into the femoral vein, a deep vein, at the saphenofemoral junction, typically 3-4 centimeters below the inguinal ligament.
The Small Saphenous Vein begins on the lateral side of the dorsal venous arch of the foot. It courses upward along the posterior surface of the leg, passing behind the lateral malleolus. This vein ascends through the calf, running between the two heads of the gastrocnemius muscle. The SSV terminates by draining into the popliteal vein, a deep vein behind the knee.
Its Role in Circulation
The function of the saphenous veins is to collect deoxygenated blood from the superficial areas of the leg and foot and transport it back towards the heart. This blood eventually reaches the inferior vena cava, a large vein that empties directly into the heart, where it is re-oxygenated.
To counteract gravity and ensure blood flows upward, saphenous veins, like other veins, contain a series of one-way valves. These valves consist of two elastic flaps of tissue that open to allow blood to pass through and then close to prevent backflow. The surrounding leg muscles also play a role, contracting and squeezing the veins to help propel blood toward the heart. The saphenous veins, being superficial, contribute to about 10% of the blood flow return from the legs, with the deeper veins handling the majority.
Common Conditions and Medical Uses
Due to their superficial location and the constant battle against gravity, the saphenous veins are susceptible to certain conditions. One common issue is the development of varicose veins, which are enlarged, twisted veins visible under the skin. This occurs when the one-way valves within the saphenous veins become weak or damaged, allowing blood to flow backward and pool, leading to increased pressure and vein distension.
This valve dysfunction can also lead to chronic venous insufficiency (CVI), a broader condition where veins struggle to effectively return blood to the heart. Symptoms of CVI related to saphenous vein dysfunction can include leg swelling, aching, heaviness, and skin changes. While varicose veins are often a visible sign, CVI signifies a problem with blood flow regulation within the vein itself.
Beyond health concerns, the saphenous vein has medical uses due to its length, accessibility, and suitable diameter. It is frequently harvested for coronary artery bypass graft (CABG) surgery. In this procedure, a segment of the saphenous vein is removed from the leg and used to create a new pathway for blood flow around a blocked coronary artery in the heart. It is a common choice for grafting due to its availability and ease of harvest.
The saphenous vein’s superficial location also makes it accessible for other medical procedures, such as intravenous (IV) cannulation, particularly when other sites are unavailable or difficult to access. This involves inserting a catheter into the vein to administer fluids or medications. While typically a last resort compared to upper limb access, the great saphenous vein, especially near the ankle, can be a viable target for rapid venous access in certain situations.