Why do you bleed (when you are injured)?
The smallest thing that makes up the human body is the cell. The human body is made up of a very large number of cells.
Cells in the body cannot operate without oxygen and nutrients. Blood is responsible for carrying such important oxygen to all parts of the body. Since blood flows through blood vessels, the blood vessels must be stretched out like a web throughout the body. The only parts of the body that do not have blood vessels are the surface of the skin, hairs, and nails. Therefore, even a slight cut on a fingertip will immediately break a blood vessel and cause blood to flow.
