The path through which the blood flows in the human body is called blood vessels.
Types of Blood Vessels
In general, the human body has three types of blood vessels. We discuss their major characteristics below:
Arteries
Arteries are the blood vessels that carry pure or oxygenated blood.
Pure blood flows under high pressure in the human body. Therefore, arteries are placed deep under the human skin. They have thicker walls to bear the high pressure of the blood.
As the blood flows under high pressure, there is little to no chance of the backflow of the blood. Hence, arteries do not contain valves.
It is important to note, however, that the Pulmonary Artery carries impure or deoxygenated blood from the heart to the lungs.
Veins
Veins are the blood vessels that carry impure or deoxygenated blood.
Impure blood flows under low pressure in the human body. Therefore, veins are placed superficially on the human skin. Consequently, they have thinner walls.
As the blood flows under low pressure, there is a chance of the backflow of the blood in the veins. Hence, veins contain valves to prevent the backflow of the blood.
It is important to note, however, that the Pulmonary Vein carries pure or oxygenated blood from the lungs to the heart.
Capillaries
Capillaries are extremely narrow and thin-walled blood vessels. They connect arterioles (branches of Arteries) to the venules (branches of Veins). These connections act as the site of transmission of various chemical substances.