Veins are superbly designed tubes with a series of one-way valves which are structured to prevent the contents, blood, from flowing any other way than forwards towards the heart when they are in good health.
When, for any of a number of reasons, a valve becomes incompetent, and allows a back-flow of blood, the vein becomes distended, its walls stretch and, like tired elastic, sag, allowing the vein to swell in that region into a miniature balloon.
This is a varicosity.
When this happens in the legs, the commonest site, it is called a varicosity, and when this occurs in the rectum it is known as haemorrhoids, or piles.
How Do Veins 'Move' the Blood?
There are a number of driving forces which are involved in the return of blood to the heart for oxygenation, along the veins.
These include the contracting and relaxing effect of muscles in which many veins lie.
As muscles work they automatically apply a pumping action to any vein with which they are in touch,and this, because of the vein's one-way valve system, causes a forward motion of the blood.
Many veins run alongside arteries (which carry fresh oxygenated to the body tissues) and the pulsating action of these arteries (due to the heart's beating) also produces a pump-like effect on the veins.
Another key pumping action occurs as we breathe, with the rise and fall of the diaphragm, which creates an alternating positive and negative pressure in the chest cavity.
Much of the blood returning to the heart has to overcome the force of gravity, for example as it passes from the feet upwards into the pelvic area and then onto the chest cavity and its destination, the heart.
While muscle pump action can be said to have most to do with the movement of blood up the legs themselves into the pelvic cavity, the passage onto the heart from the pelvis is largely the result of this alternating positive and negative pressure created by breathing.
So we have three pump mechanisms apart from the heart itself: active muscles, the pulsation of the arteries and diaphragmatic movement.
Finally we should consider the actual structure of the veins, comprising as they do layers of elastic and connective tissue fibres.
Those veins which lie deeper than the more superficial ones are usually enclosed in a sheath of connective tissue in which the arteries are resting, and the health and integrity of the connective tissue can influence the efficiency of the vein.
What Goes Wrong?
The structure of the veins themselves, the healthy constituency of the connective and elastic tissues, is directly related to nutritional factors (as is the integrity of the nervous system which controls the muscles in which many veins lie).
Nutrition: for example the levels of certain important nutrients in the diet most notably dietary fibre, vitamins C and E, and substances called bioflavonoids (which influence the elasticity of the tissues) can have a profound effect on the prevention or development of varicosities.
If much of the movement of blood along veins is dependent on muscles regularly contracting and relaxing, as well as on the diaphragm's movement, it is pretty clear that exercise, or lack of it, and breathing function as well as mechanical stress factors (see below), are bound to be massively influential in deciding on the overall efficiency of venous return.
When any of the various pumping mechanisms are inefficient, or when the structure of the supporting tissues of the veins is inadequate, there is a strong chance of veins becoming incompetent, allowing back-pressure to build up and causing a varicosity.