Final answer:
Platelets or thrombocytes are fragments of red blood cells that play a role in blood clotting and hemostasis.
Step-by-step explanation:
Fragments of red blood cells in the bloodstream are called platelets or thrombocytes. Platelets are not complete cells but rather small, disc-shaped fragments that are derived from megakaryocytes in the bone marrow. They play an important role in hemostasis, which is the process of blood clotting to prevent excessive bleeding.