Venous insufficiency is a condition where the flow of blood from the leg back to the heart is impaired. The leg veins carry oxygen deficient blood away from the legs and certain anatomical features and physiological mechanisms in the leg enable the unidirectional flow of blood to the heart.
This includes the :
- Musculovenous pump (leg blood circulation pump) where the contraction and relaxation of the leg muscles during activity compress the veins thereby pushing the blood up the vessel. The pulsating of the leg arteries also helps to keep blood flowing in the veins.
- Valves in the leg veins prevent backward flow as the blood travels back to the heart. If blood attempts to flow in the wrong direction within the vein (away from the heart) the valve closes and prevents this.
If the valves become incompetent, then blood may flow backwards (retrograde flow) and this is known as venous reflux. A blockage within a leg vein, usually by a blood clot, can also hamper the outflow of blood from the legs. Eventually blood will pool in the feet and lower legs and move very slowly or stay almost stationary. This sluggish circulation in the leg veins is known as venous stasis.
The vascular system is a continuous network. If the blood flow out of the legs are affected, then blood flowing into the legs will also be compromised and oxygen and nutrients cannot reach the tissue of the legs. Stasis of the blood also increases the chances of further and larger clot formation and eventually one of these clots can dislodge and block the arterial supply of a vital organ like the lung (pulmonary embolism).
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