This document summarizes the process of hemostasis, including platelet activation and aggregation to form a loose plug, coagulation involving prothrombin and fibrinogen to stabilize the clot, and fibrinolysis by plasmin to dissolve the clot. It discusses the roles of platelets, coagulation factors, fibrinogen and fibrin in clot formation. It also mentions how anticoagulants prevent coagulation to treat cardiovascular diseases and how fibrinolytics dissolve clots to limit tissue damage.

1. Hemostasis

2. Blood Components: Platelets
• Coagulate, form plug, prevent blood loss
• Formed by fragmentation from megakaryoctyes
Figure 16-10c: Megakaryocytes and platelets

3. Overview of Hemostasis:
Clot Formation & Vessel Repair
Figure 16-11: Overview of hemostasis and tissue repair

4. Hemostasis: Vasoconstriction & Plug
Formation
• Vasoconstriction
• Platelet activation
– Multiple factors
– Positive feedback
• Aggregation
• Loose plug

5. Hemostasis: Vasoconstriction & Plug
Formation
Figure 16-12: Platelet plug formation

6. Hemostasis: Coagulation & Clot
Stabilization
• Prothrombin
• Ca++
• Fibrinogen
• Fibrin
• Polymerization
Figure 16-13: The coagulation cascade

7. Dissolving the Clot and Anticoagulants
• Bleeding stopped
• Vessel repair
• Plasmin
• Fibrinolysis
• Clot dissolved

8. Dissolving the Clot and Anticoagulants
Figure 16-14: Coagulation and fibrinolysis

9. Coagulation and Disease
• Hemophilia
• Cardiovascular Diseases
– Key problem – clots block undamaged blood vessels
– Anticoagulants prevent coagulation
• Keep platelets from adhering
• Prevent fibrin coagulation
– "Clot Busters": Prevent further clotting
• Speed fibrinolysis
• Limit tissue damage (heart, brain…)

10. Summary
• Blood is about 50% plasma, water solvent &
solutes: ions, elements, gasses, proteins, wastes
& nutrients
• White blood cells function in internal defense
• Iron in hemoglobin is key to RBC transport of O2
• Platelet activation initiates clot formation
• Clotting prevents blood loss but is a problem in
cardiovascular disease