Answer:
The circulatory system of the human body consists of three types of vessels which carry blood. These blood vessels have been distinguished on the basis of structure and function and called arteries, veins and capillaries.
Structure
1. Lumen diameter: Arteries have a large diameter as compared to veins and capillaries and capillaries has the smallest diameter in all of these.
2. Wall thickness: Arteries have the thickest wall than veins and capillaries have the thinnest wall.
3. Wall layer: arteries and veins made of three layers of muscle whereas veins made of one layer of cells.
Function
1. Arteries: brings oxygenated blood (oxygen-rich) from the heart to the body parts in pulses
2. Veins: carry deoxygenated blood from the body to the heart
3. Capillaries: carry both oxygenated and deoxygenated blood away from the body.