The origin of the word Vena is Latin and it is the same word itself, it was used to refer to those conduits through which something can flow or pass, generally water; At present, this reference is still used, for example when a well is being dug in order to obtain water, when it is obtained it is said that it is through a vein of said substance. In most cases, the word vein is used to refer to the conduits that the body has for the blood to pass from the blood capillaries or organs to the heart. Veins are also known as blood vessels and have the ability to carry non-oxygenated blood, because it is oxygenated once it passes through the lungs, since the blood contained in them is oxygenated.
Veins are an important part of the circulatory system because they have 70% of the total blood volume, thus being called high capacity vessels. In addition to conducting blood, veins are characterized by also transporting carbon dioxide and the waste that the body may have, collecting them from the tissues and taking them to the organs capable of eliminating them, such as the kidneys and lungs.
The veins are formed by three layers that make up the wall, which are divided into an internal layer called endothelial because consists of endothelial cells, the layer of the medium is muscle because the fibers comprise conjunctive and muscle cells and the outer layer called adventitia, which is likewise constituted by muscular conjunctive fibers.
It must be borne in mind that veins are different from arteries, for example, the walls that make up the veins are more fragile because they are less thick than the arteries, and the veins are closer to the skin than the arteries and the location of them in the body is not precise, that is, it varies from one person to another. The veins could present different pathologies such as varicose veins (they do not allow the blood to return normally to the heart), thrombosis (they are blood clots inside the veins), inflammations, etc.
