Types of Blood Vessels
Arteries are vessels that carry oxygen-rich blood from the heart to all organs and tissues under high pressure.
Veins are vessels that carry blood back to the heart and lungs. The pressure in them is relatively low (lower than in the arteries), but sufficient to overcome the force of gravity.
There are two parallel pathways for blood to drain from the lower extremities. Outflow through the deep veins, due to muscle activity, and outflow from the superficial veins upward and into the deep veins through the perforating veins.
Perforating veins are intermediate veins between the deep and superficial veins. With the help of perforating veins, both networks communicate with each other. Blood normally flows from superficial veins to deep veins, and blood flow from deep veins to superficial veins is considered pathological.
Valve disorders of veins
There are many valves along the lumen of superficial veins. The most important of them are located in the area where superficial veins flow into deep veins, i.e. in the popliteal fossa and in the groin area.
The valves can be damaged. As a result, their flaps are deformed, which leads to a reverse flow of blood down the veins, stagnation and subsequent expansion of the veins.