Artery Vs. Vein

Everyone has heard about arteries and veins in the body, but how do they differ? Both are essential components for human life, and need to be functioning in perfect working condition.
It is crucial to understand the differences between arteries and veins when one is dealing with the human blood circulatory system. These are 2 primary components of this system, and they are both distinctly different from each other. The task carried out by both are mostly identical in nature, except for a few differences here and there.
The primary difference between the two is the direction in which they carry and transport the blood within the body. The arteries carry blood from the heart to the other body parts. This fresh blood contains oxygen and thus revitalizes the parts that it reaches. On the other hand, the veins carry impure blood back to the heart, so that it can be reprocessed and re-injected with oxygen by the lungs. This blood carried by the veins does not have oxygen in it, and therefore, together, both perform a crucial function for the survival of the human body.
Structural Difference
Though both blood vessels simply transport blood from one part to another, their structures are slightly different from each other. Arteries are larger than veins, and carry greater elasticity as well. This elasticity is essential for them to function, and it is allowed by the connective fibers that exist in their walls. The reason arteries need greater elasticity is because they transport blood with a greater force than the veins, since the blood is constantly being 'pumped' out by the heart.
Both arteries and veins have three layers in them, and the outer layer and the inner layer are similar in structure. The inner layer is quite smooth, and the outer layer is quite thin. It is the middle layer where the difference arises, as the middle layer of an artery is far more muscular (or stronger) than that of a vein.
Pulmonary Artery and Pulmonary Veins
The pulmonary artery and the pulmonary vein carry out slightly different tasks than the rest of the blood vessels, respectively. These are the blood vessels that connect the heart to the lungs, and regulate and circulate the transfer of blood between the 2 organs.
While the pulmonary arteries carry de-oxygenated blood from the heart to the lungs (unlike all the other arteries in the body), the pulmonary veins carry oxygenated blood from the lungs to the heart. Unlike all other veins, these are the only ones in the body that carry oxygenated blood. There are 2 pulmonary arteries in the body, and 4 pulmonary veins.
The transfer of oxygenated and de-oxygenated blood from the lungs to the heart, and vice versa, and from the heart to various parts of the body, and vice versa, is an essential component of the body's existence. This blood carries oxygen which is essential to the functioning of human life, and the arteries and the veins are thus classified as the most important components of the human blood circulatory system. Moreover, when a doctor takes blood from the body to carry out medical tests, it is almost always taken from the veins, which are easily accessible. In some rare cases, blood is drawn from the arteries, but this is only under strict orders from a medical expert. Taking blood from the arteries can cause various medical complications. A doctor will study these blood vessels in order to determine the causes of poor circulation.
Pulmonary artery and vein
Blood vessels diagram