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Chapter 10 Alterations in Hemostasis. Hemostasis. Stopping blood flow Normal: Blood usually fluid Seals broken blood vessels Abnormal: Inappropriate clotting Insufficient clotting. Platelets (Thrombocytes). Thrombopoietin Made in liver, kidney, smooth muscle, bone marrow - PowerPoint PPT Presentation
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Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 10Alterations in Hemostasis
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Hemostasis
• Stopping blood flow• Normal:
– Blood usually fluid– Seals broken blood vessels
• Abnormal:– Inappropriate clotting– Insufficient clotting
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
All but which of the following are true about platelets?a. An enzyme called erythropoietin stimulates their
production. b. They are made from megakaryocytes.c. They originate from the bone marrow.d. They are stored in the spleen.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
a. 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).
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Coagulation Factors
• Plasma proteins – Most are synthesized by liver– von Willebrand factor made by endothelium– Circulate as inactive procoagulation factors
• Calcium
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
What is the effect of von Willebrand disease on the platelets?
a. Increased platelet aggregationb. Decreased platelet aggregationc. Increased platelet formationd. Decreased platelet formation
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
b. Decreased platelet aggregationRationale: 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.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Vessel Spasm
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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?
COX-1 COX-2
arachidonic acid
thromboxane A2 prostacyclin
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Intrinsic and Extrinsic Pathways
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Fibrinogen Fibrin
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
ScenarioA 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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Hypercoagulability• Increased platelet number• Platelet aggregation• Endothelial damage• Increased procoagulation factors• Decreased anticoagulation factors
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Tell whether the following statement is true or false.Hypercoagulability states increase the risk of thrombus
formation.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
TrueRationale: 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.”
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
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?
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Platelet Disorders
• Decreased platelet levels (thrombocytopenia)– Decreased production– Increased destruction– Platelets used up in forming clots
• Impaired platelet function
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question
Tell whether the following statement is true or false.Platelet disorders are bleeding disorders.
Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer
TrueRationale: 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.
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