Physiology of the venous system in the lower limbs

The main purpose of the venous system within the general circulation, is to carry oxygen-depleted blood rich in cell metabolism waste back to the heart.
It is within the legs that the stresses are the greatest and the specific characteristics of the venous system are the most important, since the venous system must move blood against the force of gravity in the standing position .

anti-reflux valves A combination of two main actions ensures venous return in the lower limbs:

  • Firstly, the presence of mobile anti-reflux valves and the resistance of the vein walls allowing the blood to move in one direction only : from the superficial to towards the deep venous system and from the feet to the heart.
  • Secondly, a pump mechanism which activates and maintains the blood flow through the veins.

The anti-reflux valves allow fluid to circulate in one direction only, making it possible to maintain the normal direction of venous blood flow, even in the absence of pressure – or in the event of negative pressure – and thereby prevent backflow of the blood.
Normal blood flow is directed from the superficial towards the deep system and from the most distal part of the body towards the heart.

The pump mechanism mainly results from a combination of different forces:

  • The stimulation of the venous system of the foot
  • The muscle pump, more specifically, the muscles of the calf (leading to alternate opening and closing of the valves): which is the main driving force behind the pump mechanism,
  • The beating of the heart and the negative pressure due to the phenomenon of aspiration from the abdominal cavity that occurs during deep breathing.
When walking, all these mechanisms work together to ensure good venous return. (read more...)
Conversely, at rest, the stimulation of the venous network of the foot and calf-muscle pump is absent. Only the impact of the heart and respiratory movements on the venous system is present. (read more...)