H5

Question 1

Define haemostasis

Answer 1

Coagulation that occurs in a physiological setting and results in sealing a break in the vasculature

Question 2

Name the vitamin K dependent factors

Answer 2

Procoagulants: Factors II, VII, IX, X
Anticoagulants: Protein C and S

Question 3

What are the components of the classic coagulation cascade?

Answer 3

• Intrinsic pathway: damaged surface
• Extrinsic pathway: trauma
• Final common pathway: thrombin converts fibrinogen into fibrin
• Tissue factor initiates coagulation cascade

Question 4

What are the components of the cellular model of coagulation?

Answer 4

• intrinsic pathway: amplifies thrombin production
• extrinsic pathway: initiates thrombin generation
• common pathway: propagation (mutiplication) of thrombin generation

Question 5

Name 4 anti-coagulants

Answer 5

1. TFPI –tissue factor pathway inhibitor - inhibits extrinsic pathway
2. AT- antithrombin - inhibit thrombin and factor x-
3. PC – protein c
4. PS – protein s

Question 6

What occurs during primary haemostasis?

Answer 6

Formation of primary plug (to plug off small injuries)

Question 7

What are the 3 main events in primary heamostasis?

Answer 7

• Platelet adhesion: platelets adhere to subendothelial matrix
• Platelet activation: once platelets adhere, become activated and recruit additional platelets to injured site
• Platelet aggregation: fibrinogen forms bridges between activated platelets to form platelet plugs, plug is unstable and disintegrates easily unless reinforced

Question 8

What occurs during secondary haemostasis?

Answer 8

Formation of insoluble, cross-linked fibrin by activating coagulation factors

Question 9

What is the sequence of events during secondary homeostasis?

Answer 9

1. Initiation of thrombin generation
2. Amplification of thrombin generation
3. Propagation of thrombin generation
4. Stabilization - fibrin formation

Question 10

What is Virchow’s triad?

Answer 10

Describes a combination of features that contribute to thrombosis:

• changes in blood flow
• changes in vessel wall
• changes in blood composition

Question 11

What are the 2 thrombotic disorders?

Answer 11

• Arterial thrombosis

- Venous thrombosis

Question 12

What are the features of arterial thrombosis and examples?

Answer 12

• platelet-rich
• high shear forces
• white
• E.g] Acute MI and Ischaemic stroke

Question 13

What are the features of Venous thrombosis and examples?

Answer 13

• Fibrin and RBC rich
• Low shear force
• Red
• E.g] Deep venous thrombosis and pulmonary embolism