When you cut your finger, blood flows from tiny vessels in your skin.
This blood helps wash out the dirt and germs that may be there from the object that did the cutting.
However, the bleeding soon stops because the blood thickens, or clots.
The clots keep out harmful bacteria and soon form a scab. The scab acts as protection while the wound is healing.
When the cut is completely filled in, the scab falls off and new skin grows.