Lower limb veins refer to the blood vessels of the lower limbs of the human body, which are divided into deep and shallow groups, as well as the lower limb communicating veins and lower limb muscle veins between the deep and shallow veins.The superficial vein will eventually flow into the deep vein.The physiological function of human veins is to ensure that venous blood flows from far to near.
Lower limb muscle contraction is an important condition to promote the centripetal flow of venous blood.During contraction, the venous valve is opened, and the valve of the perforating branch is closed, promoting blood flow to the heart;When the muscle relaxes, the venous valve shows the opposite phenomenon, and the superficial vein blood flows to the deep vein.Therefore, muscle contraction is the power of blood return, and normal valve is the condition of blood return.Therefore, lower limb veins are also called "the second heart".
The deep veins of the lower limbs are all accompanied by the same artery. The deep veins of the lower legs, namely, the anterior tibial, posterior tibial and peroneal veins, are in pairs. They run along both sides of the same artery and flow into the popliteal vein, mostly one. They continue upward as the superficial femoral vein, converge with the deep femoral vein at the groin (the root of the thigh) to form the common femoral vein, and then continue upward as the external iliac vein.
Superficial vein
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The superficial veins of lower limbs include the great saphenous vein andSaphenous vein。
The great saphenous vein is the longest subcutaneous vein in the whole body. It starts from the dorsal vein arch of the foot on the medial side of the foot, goes up along the lower leg and the medial thigh through the front of the inner malleolus, and then flows into the common femoral vein after collecting the superficial abdominal wall vein, the superficial pudendal vein, the medial femoral vein, the lateral femoral vein, and the superficial circumflex iliac vein at the groin.
The small saphenous vein starts from the dorsal venous arch of the foot on the lateral side of the foot, goes up along the posterolateral side of the lower leg through the rear of the lateral malleolus, reaches the upper segment of the lower leg, and passes throughDeep fasciaIt drains into the popliteal vein.Its branches anastomose with the branches of the great saphenous vein to form a superficial venous network.
There are many communicating veins (also called communicating branches) between the great saphenous vein and the small saphenous vein and the deep vein. Generally, there is one communicating branch in the upper part, middle part and knee of the thigh.The lower leg also has 3-4 traffic branches, mostly located at the inner ankleSupramedial malleolus4 refers to the middle of the lower leg.
venous valves
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There are many valves in deep and superficial veins and communicating veins,valveGenerally, it is located at the distal side of the main branch of the vein, and its function is to ensure the one-way return of venous blood.
The number and location of deep venous valves in the lower limbs vary from person to person.The general rule is that there are more valves at the distal end of the vein branch junction.The most constant valves are located in the deep femoral vein and the superficial femoral vein, each with a pairvalve；The second pair of valves of the superficial femoral vein are mostly located about 10 cm below the first pair of valves;There is usually a pair of common femoral veins, which are located at the proximal end of the common femoral vein;There are two pairs of valves in the popliteal vein.The number of valves in other veins is large and not constant.
Venous valves are formed by venous intima folds, and most of them are two corresponding and symmetrical valve leaves, that is, double valve type.Each valve leaf has a free edge and an attachment edge. In the double valve type, the junction of the free edge and the attachment edge is the intersection point of the two valve leaves.Most of the venous distention near the valve attachment edge isvenous sinus。Through in vitro mechanical test, the highest pair of valves of superficial femoral vein is the strongest, which can withstand 350~420mmHg reverse pressure.In the superficial venous systemvenous valves (A pair of valves before the great saphenous vein flows into the common femoral vein) is the strongest, but only 180~250mmHg, and the valve below it is weaker.Under normal circumstances, when blood flows back to the heart, the valve is attached to the vein wall, and the vein is unobstructed.When the venous pressure increases due to standing or other reasons, under the impact of reverse blood flow, the two valve leaves open and the free edges close to prevent blood reflux.At this time, the venous sinus is swollen and looks like a bamboo knot.
Lower limb veins
The lower limb vein valve is different from the heart valve, its activity is affected by many factors.Centripetal return of venous blood of lower limbs, exceptpleuralIn addition to inspiratory movement and negative pressure suction generated during cardiac diastole, it mainly depends on the squeezing effect of calf muscle pump, and with the help ofvenous valves The one-way opening function ofSuperficial veinFlow to deep veins.The one-way opening function of the valve is of great significance, which effectively prevents the backflow of blood when the calf muscle relaxes.It ensures the blood return when the human body is upright.
