Coagulation

Question 1

Outline briefly the stages of coagulation

Answer 1

1. Vascular spasm
2. Platelet plug
3. Coagulation

Question 2

Outline the process of vascular spasm

Answer 2

• Cells release chemicals
• Nerves
• Myogenic spasm

Question 3

Outline the process of platelet plug formation & inhibition

Answer 3

• Platelets (1a,1b,2b,3a) adhere to damaged subendothelium
  
  • 1a - Collagen 1,2&3
  • 1b - vWF & microfibrils
  • 2b/3a - vWF & fibrinogen
• Form monolayer, spheres & release a & b granules
  
  • ⇒ ADP, thromboxane A₂ & 5HT
  • ⇒ Aggregation & vasoconstriction
• Inhibited by PGI₂ & NO
  
  • Inhibits vasoconstriction
  • Inhibits ADP, TcA₂ & 5HT release

Question 4

Draw the coagulation cascade

Include;

• The cascade
• Label tenase & prothrombinase complex, hagemen factor, thromboplastin, thrombin, factor 3 & K+ dependant factors
• Which factors are transglutaminases/ serine proteases?
• Label the extrinsic, intrinsic & common pathways and what is used to measure them

Answer 4

See diagram.

• activated partial thromboplastin time (aPTT) asseses intrinsic & common pathway
• prothrombin time (PT) asseses extrinsic pathway

Question 5

Draw the mechanisms of inhibition of the coagulation cascade

Incude mechanisms of Heparin, Warfarin & rtPA

Answer 5