Hemostasis

Question 1

5 Stages of Hemostasis

Answer 1

1. Vessel Spasm
2. Formation of Platelet Plug
3. Blood Coagulation
4. Clot Retraction
5. Clot Lysis (Dissolution)

Question 2

Vessel Spasm

Answer 2

• Injury to vessel
• THA2 (Thromboxane 2) is released from platelets (vasoconstrictor)
• Prostacyclin from endothelium (vasodilator)

Question 3

Formation of Platelet Plug

Answer 3

• Von Willebrand factor from endothelium binding platelets to exposed collagen fibers

Question 4

Blood Coagulation

Answer 4

• 2 pathways

Intrinsic - Activation of factor XII

Extrinsic - Activation of tissue factor

Both lead to activation of Factor X

Question 5

Blood Coagulation Cont.. (Factor X)

Answer 5

Conversion of Prothrombin to Thrombin and Fibrinogen to Fibrin

Question 6

Clot Retraction

Answer 6

• Clot is formed

- Fibrin pulls out serum from clot causing it to shrink

Question 7

Clot Lysis (Dissolution)

Answer 7

• Plasminogen is still in the clot
• Release of tissue plasminogen activator (TPA) (clot buster)
• endothelium converts plasminogen to plasmin to digest fibrin strands which dissolve the clot