What Does come to Mean
A vein is a tube or blood vessel that is responsible for carrying blood from the blood capillaries to the heart . It usually carries waste from organisms and CO2, although some veins carry oxygenated blood (such as the pulmonary vein ).
Unlike arteries , the precise location of veins varies greatly from individual to individual. Veins, on the other hand, are located more superficially than arteries (that is, closer to the skin ). Another difference between veins and arteries is that the former have a thinner wall.
Veins are made up of three layers: an external (also called adventitia ), a middle ( muscular ), and an internal ( endothelial ).
In addition to the aforementioned pulmonary veins (which carry oxygenated blood from the lungs to the heart), other important veins in the human body are the vena cava (which is divided into superior - receiving blood from the upper half of the body - and inferior -takes blood from the organs located below the diaphragm-), the portal vein (whose trunk is inside the liver), the jugular vein and the femoral vein .
Specifically, we can make a great classification where the veins are organized according to the system in which they act. Thus, in the first place, we find those that are part of the so-called general system, which are those through which the blood that has less oxygen circulates and does so from the capillaries to the right side of the heart. These stand out because they have a series of semilunar valves responsible for ensuring that said blood does not return to the aforementioned capillaries.
Second, there are the veins of the pulmonary system in which, as the name implies, the corresponding blood with oxygen travels from the lungs to what is the left part of the body's engine, the heart.
And finally, thirdly, we would have to talk about the veins of the portal system. These are in which the blood circulates from one capillary to another. It is important to highlight the fact that there are in turn two types of systems of this type: the hepatic portal system and the pituitary portal system.
Among the most common diseases of the veins are varicose veins (which are dilations that are characterized by preventing the normal return of blood to the heart), thrombosis (which is noticed by the appearance of a clot inside the blood duct) and phlebitis (the swelling of the walls of the veins), among many other disorders that can affect people .
In addition to all the above, we can determine that the term in question has other meanings and meanings. So that is also used to determine the mood or mood changes of a person. An example would be the following: Manuel defines himself because he has a negative streak that makes everything around him be viewed by him with pessimism and sadness.