Vascular anatomy of the lower limbs

The human lower limbs are rich in blood vessels and nerves. The blood vessels in the lower limbs supply the blood needed by the lower limbs and are connected to the arteries and veins throughout the body. The blood in the lower limb veins flows back to the lungs, and the arterial blood in the lower limbs flows back to the heart. For medical students, it is crucial to have a good understanding of the anatomical structure of the lower limb blood vessels. So what is the anatomical structure of the lower limb blood vessels? Next, let’s take a closer look at it.

1. Lower limb arteries

(i) Femoral artery The femoral artery is the main trunk of the lower limb artery. It extends from the external iliac artery, passes through the deep surface of the mid-groin, and enters the adductor canal through the femoral triangle. The femoral artery is located superficially slightly below the abdominal groove ligament, and its pulsation can be felt in living subjects. When bleeding occurs in the lower limbs, the femoral artery can be compressed here to stop the bleeding. The femoral artery divides into the superficial femoral artery and the deep femoral artery. The superficial femoral artery is the main blood supply artery to the lower limbs. The deep femoral artery is the largest branch of the femoral artery, and it further divides into the lateral circumflex femoral artery and the medial circumflex femoral artery. When the superficial femoral artery is occluded or traumatized, the blood supply to the limbs mainly depends on the deep femoral artery and its collateral circulation. The femoral artery is the most commonly used and dissected artery in clinical practice, including angiography, intraluminal arterial molding of various parts of the arteries, vascular stents, implantation of covered stents, and lower limb vascular surgery. It is also used clinically for compression hemostasis during femoral artery puncture and emergency treatment.

(ii) The popliteal artery is the direct continuation of the femoral artery in the popliteal fossa and is located deeper in the body. The popliteal artery may be injured when the femur is fractured supracondylarly. The popliteal artery is the hub connecting the thigh and calf blood vessels. There is little collateral circulation at this location, and thrombi attached to the heart wall often block the artery after detachment, causing acute arterial embolism. Because the popliteal artery is the hub connecting the thigh and calf arteries, it must be repaired and reconstructed after injury.

(iii) Anterior tibial artery and posterior tibial artery The popliteal artery passes through the popliteal fossa and branches into three main blood vessels in the lower leg: the anterior tibial artery, the posterior tibial artery, and the peroneal artery. At the inferior angle of the popliteal fossa, the popliteal artery normally divides into two terminal branches, the anterior tibial artery and the posterior tibial artery. The main trunk of the posterior tibial artery enters the sole of the foot behind the medial malleolus and gives rise to the peroneal artery at its origin. In cases of acute or chronic limb ischemia, the three arteries are usually the anastomosis sites of the lower limb arterial arch and venous arterial pulsation. When one of the three arteries is unobstructed, it means that the ischemic limb can survive, recover, and be relieved.

(iv) Dorsal artery of the pedis The anterior tibial artery transforms into the dorsalis pedis artery. It runs between the tendons of the extensor hallucis longus and the extensor digitorum longus on the inner side of the dorsum of the foot, through the space between the first and second metatarsal bones to the sole of the foot. A pulse can be felt on the lateral side of the extensor pollicis longus tendon at the midpoint of the line connecting the medial and lateral malleolus in front of the ankle joint. If there is bleeding in the foot, you can compress the dorsalis pedis artery here to stop the bleeding. In clinical practice, the strength of the dorsalis pedis artery and posterior tibial artery pulsation is often used to examine the blood supply to the extremities after lower limb artery reconstruction surgery.

2. Lower limb veins

There are abundant centripetal one-way opening valves in the veins of the lower limbs, which prevent the backflow of venous blood and ensure the one-way reflux of venous blood from bottom to top and from shallow to deep. The veins of the lower limbs are divided into two groups: superficial and deep. The superficial veins and deep veins are connected by many communicating branches and eventually flow into the deep veins.

1. Superficial veins: mainly the great saphenous vein and the small saphenous vein. The great saphenous vein originates from the medial end of the dorsal venous arch on the medial side of the foot, ascends along the medial side of the calf and the anterior medial side of the thigh through the front of the medial malleolus, enters the deep surface below the pubic tubercle, and is injected into the femoral vein. The great saphenous vein is located superficially in front of the medial malleolus and is prone to varicose veins. It is also commonly used in clinical practice for venipuncture or incision infusion. It is often used as a material for vascular arch bridges or vascular patches in vascular surgery. The small saphenous vein originates from the lateral end of the dorsal venous arch of the foot on the lateral edge of the foot, ascends behind the lateral malleolus to the popliteal fossa, penetrates the deep fascia and empties into the popliteal vein.

(ii) Deep veins: The deep veins of the foot and calf run along with the arteries of the same name, and there are two of each. The anterior and posterior tibial veins merge into the popliteal vein. Below the knee, each artery is accompanied by two veins, which ascend to the popliteal fossa to merge into one popliteal vein. It passes through the adductor tendon hiatus and becomes the femoral vein, which ascends along with the femoral artery, initially on its lateral side, then turns to the medial side, reaches the deep surface of the inguinal ligament and becomes the external iliac vein. The femoral vein collects all the superficial and deep venous blood from the lower limbs and finally flows to the heart. As shown in the following path: superficial vein of lower limb → anterior and posterior tibial vein → popliteal vein → femoral vein → external iliac vein → common iliac vein → right atrium → right ventricle. Clinically, the detachment of blood clots caused by deep vein thrombosis in the lower limbs also follows the upward pathway and eventually embeds into the pulmonary artery, causing pulmonary embolism.