Almost all veins have tiny valves that permit blood flow
ONLY towards the heart. Flows in the opposite direction are prevented by
these valves when we cough, sneeze, walk, run and in all other
conditions that cause increased venous pressure within the abdomen and
thorax..
Any kind of flaw in these valves causes a downward transmission of
increased venous pressure. In time, unprotected segments or portions of
veins become enlarged and elongated (just like the inflation of a
balloon). Sequentially arranged valves start to leak one after the other
as the vein segment above them becomes circumferentially larger, thus
preventing correct opposition of the valves. Pressure transmitted along
the defective vein causes varicose deformities in the lower healthy
veins lower along the leg.
