A vein , in anatomy, is a blood vessel that carries blood to the heart . The arteries are the vessels that carry oxygenated blood from the heart to the tissues . Veins have less thick muscles than arteries and are generally closer to the skin.
The cardiovascular system is made up of the heart and blood vessels that together are responsible for the continuous flow of blood throughout the body. Blood circulates in the cardiovascular system, and its main function is to transport oxygen to the cells that make up the body. This system is made up of a series of blood vessels, arteries and veins that are like tubes that contain and transport blood.
The main difference between arteries and veins consists in the fact that the arteries are small and whitish and originate in the two ventricles of the heart, while the veins originate in the atria and are larger and dark red in color. They have very different tasks in the blood circulation.
What are arteries:
The arteries are the blood vessels that carry oxygenated blood from the left ventricle of the heart to the other organs (eg, the artery of the aorta) and from the right ventricle of the heart they carry the little oxygenated blood to the lungs(eg: pulmonary arteries); the larger arteries branch into smaller and smaller arteries, until they form the tiny blood capillaries. Compared to veins, they are smaller and whitish, but have a thicker wall and are subject to higher pressure: this is due to the heart violently pushing blood into the arteries to reach the entire body. In addition to being strong, the arteries must also be very elastic both to resist the push of the heart and to be able to redistribute the same push to the blood.
Examples of arteries
Among the examples of arteries we can name:
- The aorta
- The pulmonary artery
- The subclavian
What are veins:
The veins , which form part of the systemic circulation, are blood vessels that carry blood loaded with carbon dioxide, from the periphery of the body to the right atrium of the heart. However, in the pulmonary circulation, they are vessels that carry oxygenated blood from the lungs to the left atrium of the heart. Veins have a thinner wall than arteries and are dark red in color; When they are empty they are flaccid and flattened. They are divided into superficial veins and deep veins.
Examples of veins
Among the most important veins we can name:
- The jugular
- The coronaries
- The superior cellar
- The lower cellar
Blood Vessel System: Features
The blood vessel system is formed by the arterial and venous sides , interconnected with each other through the capillary district where tissue exchanges take place: the arteries are responsible for transporting blood from the heart to the periphery , while the veins carry blood from the periphery to the heart, with the exception of the portal vein circulation which serves to transport blood from the stomach and intestine to the liver for the absorption of nutrients.
Structure of blood vessels
An important common feature is the structure of the blood vessels : three concentric layers that, viewed from the inside to the outside of the vessel, are called the tunica intima, tunica median, and adventitia dress.
The structurs is composed of a layer of cells called endotheliocytes that connect directly with the lumen of the vessel, which is placed in contact with the average garment, formed by muscle cells, all enclosed by the adventitious garment that, instead, is formed by collagen and elastic tissue.
The structural differences are remarkable: the arteries have a much more developed average structure, made up of a minimum of three or four to a maximum of fifty layers of muscle cells arranged in an extremely orderly manner and rich in elastic elements interconnected between the different layers. To these are added two true and suitable elastic bands that are not present in the venous system, called internal elastic lamina and external elastic lamina.
This wealth of elastic and muscular fibers guarantees a sufficient elastic return to allow the blood to be propelled along the arterial circulation, taking advantage of the pressure wave.generated by cardiac contraction.
The larger arterial trunks are also equipped with their own vascular system, the vasa vasorum (literally from the Latin: vascular vessels), which penetrate their adventitious habit and nourish the arterial wall. As the arteries have high pressure in the circulatory system, they are precisely the ones that produce the pulse that reflects cardiac activity.
The structural organization is also reflected in the macroscopic aspect: during the dissection, the arteries, if they are cut, remain open and do not collapse, being compressible and deformable.
The veins must withstand much lower pressures and this is evident in their structure: without prejudice to the organization in three concentric tones, the veins are characterized by a thinner wall, with a drastically reduced muscular and elastic component compared to the vessels. The caliber of the vessel is on average greater than the thickness of the wall (in arteries it is exactly the opposite), so the veins collapse if they are cut.
By having an optimized structure to avoid having to withstand the high pressure loads to which the arteries are continuously subjected, the veins are equipped with special valves called the swallow’s nest, which embody the column of blood, preventing backflow and exploiting the action of compression. performed by the muscles to push blood from the periphery towards the heart (for example, varicose veins in the legs are due to the imperfect functioning of the venous valve system).
The venous system is much more extensive than the arterial one , and has a substantially double volume: many arteries are endowed with two accompanying satellite veins and there are venous vessels totally independent of the presence of a corresponding arterial.
Last characteristic: in general, the arteries run in depth with respect to the venous ones and are characterized by a more rectilinear , less tortuous and shorter course, which often approximates the bony planes in which they can print grooves. The veins, on the other hand, are more superficial and characterized by a greater number of communications between the vessels, called anastomoses.