A&P CH.17.5-7 PLATELETS, HOMEOSTASIS, BLOOD GROUPS

Describe the structure and function of platelets.

Cell fragments from megakaryocytes; form plugs to stop bleeding

Which chemicals are in platelet granules?

Serotonin, calcium, enzymes, ADP, PDGF, thromboxane A2.

Functions of platelet ADP, serotonin, thromboxane A2?

ADP attracts platelets, serotonin and thromboxane A2 enhance aggregation and spasm

Describe platelet formation and entry into blood.

Megakaryocytes send cytoplasmic projections into capillaries; fragments break off as platelets

What are the 3 steps of hemostasis?

Vascular spasm, platelet plug formation, coagulation.

Summarize the 3 phases of coagulation.

Prothrombin activator formed (intrinsic: inside blood, slow, many steps; extrinsic: tissue factor outside blood, fast), thrombin created, fibrin mesh forms clot

Function of von Willebrand factor and PDGF? (platelet derived growth factor )

vWF links platelets to exposed collagen; PDGF helps repair vessel wall.

Function and location of Antithrombin III and Heparin?

Both prevent clotting; antithrombin III in plasma; heparin in basophil and mast cells.

Difference between thrombus and embolus

Thrombus is a stationary clot; embolus is a moving clot that can block a vessel

Define thrombocytopenia

Low platelet count.

Relationship of liver cells, vitamin K, and clotting factors?

Liver uses vitamin K to make clotting factors.

Define hemophilia

: Hereditary clotting factor deficiencies causing bleeding.

Describe ABO and Rh blood groups; transfusion reactions.

ABO: A, B, AB, O types; Rh positive/negative. Mismatched blood causes immune reaction.

Universal donor blood type and reason?

Type O-; lacks A, B, Rh antigens.

Universal acceptor blood type and reason?

Type AB+; has no anti-A, anti-B, anti-Rh antibodies.