Platelets (Thrombocytes):

They are not cells but are fragments of large cells of bone marrow, called megakaryocytes. They do not have any nucleus or any pigment.

Number of Platelets (Thrombocytes):

One cubic millimeter of blood contains 250,000 platelets. The average life span of a blood platelet is about 7 to 8 days.

Functions of Platelets (Thrombocytes):

Platelets help in the conversion of fibrinogen, a soluble plasma protein, into an insoluble form, fibrin. The fibrin threads entangle with the red blood cells and other platelets in the area of damaged tissue ultimately forming a blood clot.