- The Intimate cassock, lined with a single layer of extremely flat epithelial cells called endothelial cells;
- The Middle cassock, an intermediate muscular layer, thinner than that of the arteries;
- The Adventitious tunic, the outermost, formed by connective tissue (supporting collagen and elastin).
The venous system of the lower limbs is composed of three elements: the deep venous system, the superficial venous system and that of the perforators, which connect the superficial system with the deep one (and not vice versa, because in a continent system the venous blood it goes from the superficial to the deep system, and also at the level of the perforating the venous flow follows this rule).
From the deep circle, then, the blood returns upwards, to the right heart, because the muscles of the calf and thigh, contracting during the movement, "squeeze" the veins of the deep circle bringing the blood upwards, against the force of gravity.
All this is favored by many valves, which are found in all the veins of the lower limbs, and which, if fully functional, open when the blood arrives and close immediately after its passage, preventing its reflux in a retrograde sense. , downward.
, venous blood is rich in carbon dioxide and waste substances, and goes from the periphery to the right heart, which will then take it to the lung to purify it of carbon dioxide and supply it with oxygen. At this point the blood becomes arterial, rich of oxygen and nutrients, and from the lung it is carried to the left heart, from where it will then be distributed to the periphery).
Two large superficial venous districts are recognized in the lower limbs, which are the Grande-Saphena vein (originating from the Femoral vein) and the Little Saphena vein. The Great Saphena drains most of the superficial circulation of the leg and thigh into the deep veins, while the Little Saphena essentially drains the posterior region of the leg always in the deep veins of the lower limb.
The Safenae relate to the deep venous systems through the perforating veins, which are about 150 in number.
During the upright position (orthostatism) the blood column (blood) exerts, at the level of the foot, a pressure that in the adult corresponds to an average value of 80-100 centimeters of water (which is a "unit of measurement of pressure). . When physical movement begins, such as walking for example (walking), the blood passes from the superficial to the deep venous circulation and, thanks to the propulsive pump mechanism of the leg and thigh muscles, there is an emptying of the deep venous circulation, with progressive fall of the pressure values to about 20 centimeters of water; following the stopping of walking, the blood pressure values tend to slowly recover, in about 30 seconds.
It is very important, to understand varicose pathology, to understand which are the haemodynamic factors that come into play in the venous return. They are:
- Vis a latere, back, front, or the strength of the muscles on the side, from behind and from the front in conditions of rest (tonic contractions);
- Muscle pump during movement (phasic contractions);
- Venous tone, or the ever-present degree of slight contraction of the vein wall regulated by the vegetative nervous system (that is, the one that regulates many functions that do not depend on our will.
Other articles on "Veins: Anatomy"
- Varicose veins
- Varicose veins: causes and classification
- Varicose veins: symptoms and diagnosis
- Varicose veins: treatments and therapy
