Name the three kinds of blood vessels found in human beings. With the help of suitable diagrams, differentiate between them.
The three kind of blood vessels found in human beings are arteries, veins and capillaries.
- Arteries are the blood vessels that carry blood from the heart to the various parts of the body.
- Veins are the blood vessels that carry blood from the body parts to the heart.
- Capillaries: These are the terminal branches of an artery, which rejoin to form a vein. A capillary is a very narrow tube whose walls have a single layer of cells with no muscles. Although the wall of a capillary is veiy thin, yet an exchange of nutrients, waste products and gases take place between the blood and the body fluids.
- Carry blood away from the heart.
- Have thick and more muscular walls.
- Carry oxygenated blood (except pulmonary artery which carries deoxygenated blood).
- The blood flows with jerks and under great force.
- Carry blood towards the heart.
- Have thin and less muscular walls.
- Carry deoxygenated blood (except pulmonary vein which carries oxygenated blood).
- The blood flows smoothly and under little pressure.
- Arteries after entering an organ divide into number of smaller branches called arterioles which further divide repeatedly to form a network of fine branches called capillaries.
- The walls of the capillaries are very thin and are one cell deep.
- The Capillaries after the metabolic exchange unite to form larger vessels called venules, which again unite to form a vein.