Chapter 10 Alterations in Hemostasis

1. Chapter 10Alterations in Hemostasis

2. Hemostasis • Stopping blood flow • Normal: • Blood usually fluid • Seals broken blood vessels • Abnormal: • Inappropriate clotting • Insufficient clotting

3. Platelets (Thrombocytes) • Thrombopoietin • Made in liver, kidney, smooth muscle, bone marrow • Megakaryocytes formed in bone marrow • Break apart to form many platelets • Platelets live 8–9 days in circulation • Many are stored in spleen • Released when needed

4. Question All but which of the following are true about platelets? • An enzyme called erythropoietin stimulates their production. • They are made from megakaryocytes. • They originate from the bone marrow. • They are stored in the spleen.

5. Answer • An enzyme called erythropoietin stimulates their production. Rationale:Erythropoietin stimulates the production of RBCs (erythrocytes). The word literally means erythrocyte production. Platelet formation is stimulated by thrombopoietin (thrombus/clot production).

6. Mediators of Hemostasis • Chemicals produced by platelets • Released at an injury to: • Start clotting by reacting with blood proteins • Help platelets stick together • Stimulate wound healing • Help platelets stick to vessel wall • Constrict blood vessels

7. Coagulation Factors • Plasma proteins • Most are synthesized by liver • von Willebrand factor made by endothelium • Circulate as inactive procoagulation factors • Calcium

8. Question What is the effect of von Willebrand disease on the platelets? • Increased platelet aggregation • Decreased platelet aggregation • Increased platelet formation • Decreased platelet formation

9. Answer • Decreased platelet aggregation Rationale:Von Willebrand disease is the most common hereditary bleeding disorder. It is caused by a deficiency or defect in vWF (which carries a clotting factor). The result of less clotting factor is an inability to clot.

10. Vessel Spasm

11. Cyclooxygenase Enzymes (COX)Produce Mediators of Hemostasis • Celebrex is a drug that blocks COX-2 • People taking Celebrex develop increased TXA2 levels • What problems might they have? arachidonic acid COX-1 COX-2 thromboxane A prostacyclin 2

12. Intrinsic and Extrinsic Pathways

13. Fibrinogen  Fibrin

14. Scenario A man had a stroke and the doctor gave him tissue plasminogen activator (TPA). • Why? What is the doctor trying to accomplish? • One of the man’s relatives wondered why they did not give him heparin or warfarin instead • What is the difference? Why might TPA be more appropriate?

15. Hypercoagulability • Increased platelet number • Platelet aggregation • Endothelial damage • Increased procoagulation factors • Decreased anticoagulation factors

16. Question Tell whether the following statement is true or false. Hypercoagulability states increase the risk of thrombus formation.

17. Answer True Rationale:Hyper- as a prefix means “over” or “too much.” Coagulation/coagulability means “clotting/the ability to clot.” Hypercoagulability means “increased ability to clot or form thrombi.”

18. Scenario: A woman with lupus develops breast cancer. • She is given radiation therapy • She begins to develop nosebleeds and bruising • Her menstrual period is abnormally heavy Question: Why did this happen?

19. Platelet Disorders • Decreased platelet levels (thrombocytopenia) • Decreased production • Increased destruction • Platelets used up in forming clots • Impaired platelet function

20. Question Tell whether the following statement is true or false. Platelet disorders are bleeding disorders.

21. Answer True Rationale:Because the platelet’s job is to clot, platelet disorders mean that the platelets cannot do that job. An inability to clot results in bleeding/bleeding disorders.