Hemostasis Blood Types Introduction Read Coagulation Disorders on

Hemostasis & Blood Types Introduction Read “Coagulation Disorders” on page 333 in your textbook and answer the following questions. 1. What is hemophilia? What is its historical significance? 2. What is von Willebrand disorder? 3. What is (ITP) Immune Thrombocytopenic Purpura? HEMOPHILIA

Hemostasis & Blood Types Explicit Instruction Hemostasis refers to the stoppage of bleeding. ◦ (1) Blood vessel spasm: cutting a blood vessel causes the muscle in its walls to contract in a reflex, or engage in vasospasm. ◦ (2) Platelet plug formation: platelets stick to the exposed edges of damaged vessels, forming a net with spiny processes protruding from their membranes. ◦ (3) Blood coagulation: a series of chemical reactions to form a blockage. ◦ Thromboplastin from damaged tissue ◦ Prothrombin activator produced ◦ Prothrombin converted into thrombin ◦ Fibrinogen converted into fibrin ◦ Fibroblasts then invade the area and produce fibers throughout the clot.

Hemostasis & Blood Types Explicit Instruction Failed transfusions led scientists determined that blood was of different types and only certain combinations were compatible. Agglutination, the clumping of RBCs, is due to the interaction of proteins on the surfaces of RBCs (antigens) with certain antibodies carried in the plasma. Only a few of the antigens on red blood cells produce transfusion reactions, including the ABO group and Rh group.

Hemostasis & Blood Types Explicit Instruction ABO Blood Group ◦ Type A blood has A antigens on red blood cells and anti-B antibodies in the plasma. ◦ Type B blood has B antigens on red blood cells and anti-A antibodies in the plasma. ◦ Type AB blood has both A and B antigens, but no antibodies in the plasma. ◦ Type O blood has neither antigen, but both types of antibodies in the plasma. ◦ Adverse transfusion reactions are avoided by preventing the mixing of blood that contains matching antigens and antibodies.

Hemostasis & Blood Types Explicit Instruction Rh Blood Group ◦ The Rh factor was named after the rhesus monkey. ◦ If the Rh factor surface protein is present on red blood cells, the blood is Rh positive; otherwise it is Rh negative. ◦ There are no corresponding antibodies in the plasma unless a person with Rhnegative blood is transfused with Rhpositive blood; the person will then develop antibodies for the Rh factor. ◦ Erythroblastosis fetalis develops in Rhpositive fetuses of Rh-negative mothers but can now be prevented.

Hemostasis & Blood Types Independent Practice 1. What is hemostasis? 2. How does a blood vessel spasm help control bleeding? 3. Describe the formation of a platelet plug. 4. Review the major steps in blood clot formation. 5. What are antigens and antibodies? What are their role in human immune response? 6. What is the main concern when blood is transfused from one individual to another? Why does this happen?