Platelets

• Platelets are flattened, membrane enclosed cytoplasmic packets circulating in the bloodstream
• Platelets are from cells called megakaryocytes from normal red bone marrow
• During their development and growth, megakaryocytes manufacture structural proteins, enzymes, and membranes. Then platelets are formed by shedding cytoplasm
• Platelets continually replaced, an individual platelet circulates for 10-12 days before being phagocytized
• An abnormally low platelet count is known as thrombocytopenia
• Thrombocytosis is an abnormally high platelet count
• Hemostasis prevents the loss of blood through the walls of damaged vessels
• Functions of platelets

  • controlling the clotting process by releasing enzymes and other factors at appropriate times
  • clumping together at an injury site to form a platelet plug that slows the rate fo blood loss while clotting occurs
  • containing actin and myosin filaments that interact and shorten during clotting process