I am not a whole cell, but rather i am a very small, irregularly shaped particle that promotes blood clotting (in purple) and wound healing, where over a trillion of us exist in the average human blood. i am a:

The correct answer is platelets or thrombocytes.

Platelets are a component of blood whose function together with the coagulation factors is to initiate a blood clot after the injury. Even though platelets are not cells, they are fragments of cytoplasm derived from the megakaryocytes. Platelets are found only in mammals.