Blood platelets, also known as thrombocytes, are even smaller than red blood cells. They are cytoplasm fragments protected by a cell membrane.

Like other blood cells, platelets, are formed in the bone marrow. They play a very important role in the complex process of blood coagulation. 

Blood coagulation helps to stop wounds from bleeding. When platelets are damaged, they release an enzyme into the blood. This enzyme converts a protein called fibrinogen into fibrous fibrin. Vitamin K is also required to produce this enzyme. The fibrin strands adhere to the edges of the wound. The blood cells that become attached to the fibrin strands gradually accumulate near the opening, blocking the wound.

Finally, the strands retract and squeeze out all excess fluid. A scab is created, which is like a patch on our body and should not be plucked. The scab comes off when the skin has completely repaired the wound below it.