Veins , like arteries , are blood vessels . For a long time, these vessels were defined as blood vessels that carried blood rich in carbon dioxide, also called venous blood. However, this is not true, since the pulmonary veins are responsible for transporting blood rich in oxygen, the so-called arterial blood. The best definition of a vein, therefore, is the one that presents it as a blood vessel whose function is to ensure that the blood , present in various tissues of the body, returns to the heart.
The veins have a wall formed by three layers : tunica intima, tunica media and tunica adventitia. This wall is less developed than the arterial wall, being about 1/3 the thickness of an artery wall. Veins carry blood at low pressure, and, to ensure the return of blood to the heart, they have valves . In certain situations, these valves can present problems, triggering the appearance of varicose veins .
Characteristics of the veins
Veins are important blood vessels that promote the return of blood to the heart. They can be classified, according to their caliber, into: small, medium and large, most of them being small or medium caliber , with a diameter of 1 mm to 9 mm. Veins have three layers forming their walls, just like arteries. The wall of veins, however, differs from that of arteries because it is thinner. In arteries, the presence of thick walls is essential to withstand high blood pressure, which is not observed in veins, in which blood flows at low pressure. The layers that form the wall of the veins are:
- Tunica intima: it is an inner layer and is formed by endothelial cells , which are supported on a loose connective tissue . This layer is generally thin. However, in large veins, the tunica intima is well developed.
Tunica media: in it we observe, mainly, cells of smooth muscle tissue. A matrix with different components, such as elastic and reticular fibers, is also observed. It is worth noting that, when compared to the tunica media of the arteries, this layer has fewer muscle cells and also a smaller amount of elastic fibers.
- Tunica adventitia: in it, the presence of mainly elastic fibers and collagen is verified . It is a layer more developed in veins than in arteries.
As mentioned, veins are blood vessels that have the function of returning blood from the tissues to the heart. This return is not always easy, since, in these vessels, the blood is under low pressure and, many times, the return must happen against the action of gravity.
To ensure this return, the veins have valves that help maintain the unidirectional flow, thus preventing the backflow of blood . These valves are folds of the tunica intima that project into the vessel and are shaped like a half moon. In addition to the action of the valves, the vein ensures the return of blood thanks to contractions of the smooth muscle present in its wall and contractions of the skeletal muscles that surround the vein.
Characteristics of veins: – venules
Characteristics of veins: Venules are vessels that collect blood from capillaries and have a diameter of 0.1 mm to 0.5 mm. They form through the fusion of capillaries and progressively come together to form veins.
Classification of veins
Veins can be classified into deep and superficial. Superficial veins are those that run above the muscle fascia and can be seen through the skin. They are more caliber in the limbs and neck. Due to their location, they can be used as access routes for punctures. In people with developed muscles, these veins can be seen easily.
The deep veins, in turn, are located more internally, being found transiting below the muscular fascia. They can be arranged to follow the arteries or be alone.
Varicose veins and blood circulation in the veins
Veins are blood vessels through which blood circulates under low pressure, which makes unidirectional flow difficult. The valves of the veins act, in this context, preventing blood reflux. In certain situations, however, these valves are defective , which ends up impairing the flow of blood and causing dilatations in the veins due to the accumulated blood. These veins, called varicose veins , are tangled and tortuous.
Varicose veins commonly appear in the legs, and the development of varicose veins is related, for example, to standing for long periods .
Teachers are strong candidates to develop the problem due to the fact that, during work, they move little, remaining for long periods standing or sitting. Without muscle contraction in the legs and feet, blood flow is impaired, which can lead to the formation or worsening of varicose veins. Pregnant women and overweight people are also more likely to develop the problem. It is worth noting that varicose veins are apparently associated with a genetic predisposition.
Varicose veins can trigger unpleasant symptoms in the patient, such as swelling, heaviness in the legs, burning sensation in the legs and cramps . If left untreated, varicose veins can progress and cause darkening of the skin and even ulcers (sore formation).
The treatment of varicose veins can involve different techniques, of which we can highlight chemical sclerotherapy, surgery, laser sclerotherapy, endovenous laser, and radiofrequency. It is worth noting that each technique will be chosen according to each patient’s condition, therefore, the evaluation of an angiologist is essential.