Concept in Definition ABC

The veins are conduits that are part of the circulatory system, whose function is to conduct blood from the tissues to the heart. The veins on their way converge to each other, giving rise to ever-growing vessels. diameter, until forming the vena cavae, superior and inferior, as well as the pulmonary veins, which collectively collect blood from the body.

The circulatory system has the function of distribution of blood in the body. The blood contained in the heart reaches the different tissues through the arteries, once deoxygenated it returns to the heart through the veins.

In the case of pulmonary circulation, the oxygen-depleted blood that reaches the right atrium through the vena cava passes to the ventricle right and from there it is carried to the lungs by the pulmonary arteries. Once oxygenated, the blood returns to the left atrium through the pulmonary veins, from where it passes to the left ventricle to be sent to the rest of the body through the aorta artery.

Veins have a different structure than arteries

Although arteries and veins are responsible for the distribution of blood throughout the body, both have completely different structures.

The arteries are made up of an inner layer or endothelium, a middle layer made up mainly of muscle fibers, and an outer lining layer. The veins, for their part, lack endothelium and their muscular wall is much thinner than that of the arteries, in addition to this they Veins inside contain a system of valves that prevent blood from flowing backward, that is, it is return.

The variation in the muscular layer is related to the fact that the arteries are structures that work with blood under pressure, while the venous system works with low pressure and in a large part of its path against gravity, which is why it requires the presence of valves in order to prevent the backflow of blood.

Main venous systems of the body

The return of blood to the heart occurs by the confluence of several venous systems, these correspond to:

Venous system of the legs.

It contains a large number of venous blood vessels that converge, originating two main systems: the superficial venous system, which runs under the skin, and the deep venous system, which runs between and under the muscles. Both systems converge, originating the femoral vein, which at the level of the pelvic cavity continues with the external iliac vein, to which the venous trunks of the pelvis join to form the vena cava lower.

Portal venous system.

The blood coming from apparatus digestive contains the nutrients and various substances that enter the body with foodFor this reason, this blood is collected in a special venous system that gives rise to the portal vein, a structure that carries this blood to the liver, where these substances are filtered and processed. The blood that leaves the liver does so through the suprahepatic veins, which drain into the inferior vena cava.

Venous system of the upper limbs, head and neck.

The veins originating in these structures give rise to large venous trunks that correspond to the axillary vein, jugular veins and subclavian veins that will converge, originating the vena cava higher.

Pulmonary venous system.

The blood that reaches the heart contains a low amount of oxygen and a high amount of carbon dioxide from the tissues as the end product of the metabolism. This blood is taken to the lungs for oxygenation, being returned to the heart through the pulmonary veins.

Photos: Fotolia - blueringmedia / angelmaker

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