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Y2 Pathology > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

What are the 2 main functions of haemostasis?

A

Maintenance of:

  • vascular integrity
  • blood fluidity
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2
Q

What factors are involved in haemostasis?

A
  • Blood vessels
  • Platelets
  • Von Willebrand Factor
  • Coagulation cascade
  • Fibrinolytic mechanisms
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3
Q

What is primary haemostasis?

A

Formation of the primary plug

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4
Q

What are the first steps involved when there is vascular endothelial damage?

A
  • Exposure of sub-endothelial collagen
  • Release of P-selectin inducing ‘rolling’ of platelets and leucocytes
  • Release of von Willebrand factors which bind to collagen and platelets
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5
Q

How does platelet-endothelium adhesion occur?

A

Via GPI receptor who binds to von Willebrand factor or collagen, enabling platelets to adhere to the damaged endothelium

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6
Q

How does platelet aggregation occur?

A

Platelet-platelet via GPIIb/IIIa receptor through fibrinogen of vWF bridges

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7
Q

What can platelets secrete following activation?

A
  • Thromboxan
  • Serotonin
  • factorV
  • ADP
  • ATP
  • Plasminogen
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8
Q

How does clot retraction occur?

A

Activated platelet, interplatelet bridging via fibrinogen and platelet myosin+actin undergo a contractile process that cause clot retraction which facilitates wound closure

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9
Q

What is the von Willebrand structure, and what is it involved in?

A
  • Large multimeric plasma protein produced by endothelial cells
  • Involved in platelet adhesion and aggregation
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10
Q

von Willebrand structure is secreted as a carrier of which factor?

A

Factor VIII

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11
Q

What is secondary haemostasis?

A

Formation of the definitive clot - coagulation

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12
Q

How is the definitive clot formed?

A

Conversion of soluble fibrinogen to insoluble fibrin mediated by thrombin (activation sustained by the coagulation cascade)
Fibrin cross linkage forms a mesh that makes the platelet plug more stable

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13
Q

Define the role of the coagulation cascade

A

Interconnected series of enzyme activated steps resulting in the formation of thrombin (factor IIa) and insoluble fibrin

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14
Q

The factors of the coagulation cascade are in the order of?

A

When they were discovered

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15
Q

Which of the factors is fibrinogen, and which is fibrin?

A

Factor I

Activated form Factor 1a

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16
Q

Which of the factors are the following:

  • Free Ca ions
  • Prothrombin
  • Tissue factor
  • Thrombin
A
  • IV
  • II
  • III
  • IIa
17
Q

Most steps of the coagulation cascade involve?

A
  • an enzyme, substrate and cofactor
  • assembled and localised on a phospholipid surface
  • with free calcium ions
18
Q

Which factors are involved in the intrinsic and extrinsic pathways?

A 
Extrinsic = Factor VII + tissue factor as an activator 
Intrinsic = XII, XI, IX, VIII
19
Q

Describe the common pathway and the factors involved

A
  • Xa, Va and free calcium on a phospholipid surface form the prothrombinase complex
  • Converts II into IIa (prothrombin into thrombin)
  • This converts I into Ia (fibrinogen into fibrin)
  • Amplifies coagulation
  • The common pathway is the end of both the intrinsic and extrinsic pathway
20
Q

The PTT tests for which pathways?

A

Intrinsic and common

21
Q

The PT tests for which pathways?

A

Extrinsic and common

22
Q

Where are the coagulation factors produced?

A

In the liver

23
Q

Which factors are vitamin K dependant?

A

II, VII, IX, X

24
Q

Which factors are non-enzymatic?

A

Factor III - tissue factor
Factor I (fibrinogen)
Factor V
Factor VIII

25
Q

What do the vitamin K dependant factors rely on for activity?

A

Carboxylation in the liver - need to bind to free calcium ions

26
Q

Why don’t we turn into a big clot?

A
  • Dissolution of the clot, fibrinolysis

- Natural anticoagulants

27
Q

Describe tertiary haemostasis

A
  • Fibrinolytic pathway
  • Starts when coagulation starts
  • Lysis of platelet-fibrin network
  • Degrades fibrin to fibrin degradation products including D-dimers
28
Q

Tertiary haemostasis is mediated by?

A

Plasmin

29
Q

What is the major anticoagulant?

A

Antithrombin III

30
Q

Which molecule enhances the action of antithrombin III?

A

Heparin

31
Q

What are other natural anticoagulants?

A
  • Intact endothelium
  • Protein C
  • Tissue factor pathway coagulation inhibitor
32
Q

Which factor starts the intrinsic pathway?

A

Factor XII

33
Q

What is the end product of secondary haemostasis?

A

Cross-linked fibrin

34
Q

Which factor is activated by the intrinsic and extrinsic pathways?

A

Factor X

35
Q

Haemophilia A is a deficiency of factor VIII, which test result would be altered?

A

PTT

36
Q

In severe liver insufficiency, which test results can be altered?

A

PT, PTT, fibrinogen conc

Y2 Pathology (33 decks)

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