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103 Theme 2 > Lecture 2: Haemostasis > Flashcards

Lecture 2: Haemostasis Flashcards

1
Q

what do endothelial cells do

A
  • when intact, prevents clots
  • when injured, promotes local clotting
  • signals inflammatory cells to areas needing defence / repair
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2
Q

what is haemostasis

A
  • stopping bleeding
  • clotting and stopping blood from escaping
  • first stage of wound healing
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3
Q

what are the platelet based pathways to repair blood vessels

A
  • platelet adhesion
  • platelet activation
  • platelet aggregation
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4
Q

what are the non platelet based pathways of haemostasis

A
  • enzyme cascade of coagulation

- vasoconstriction

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5
Q

what are the vasoconstrictors released by platelets

A
  • serotonin
  • ADP
  • thromboxane A2
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6
Q

where are megakaryocytes found

A

bone marrow

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7
Q

what is low platelet count called

A

thrombocytopaenia

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8
Q

what happens during platelet activation

A
  • platelets exocytose serotonin, ADP and calcium
  • increase respiratory rate
  • change shape to have protruding pseudopodia
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9
Q

what do platelets adhere to

A

exposed collagen

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10
Q

what is aggregation stimulated by

A

ADP

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11
Q

what is aggregation blocked by

A

Prasugrel

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12
Q

how do platelets aggregate

A

via fibrinogen

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13
Q

which clotting factors are not enzymes

A

factor V and VIII, as they are cofactors

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14
Q

what is an example of a thrombus

A

atrial fibrillation leads to thrombosis which leads to a stroke

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15
Q

what are examples of anticoagulants

A
  • heparin

- citrate

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16
Q

what is serum and how is it different to plasma

A
  • fluid left in blood after clotting

- lacks fibrinogen, clotting factors II, V and VIII

17
Q

what does the extrinsic pathway of coagulation do and require

A
  • requires secretion of tissue factor

- initiates coagulation

18
Q

what does the intrinsic pathway of coagulation do

A
  • all factors / proenzymes are already in place

- amplifies process through positive feedback

19
Q

which factors activate thrombin

A
  • factor Xa poorly activates it

- factor Va and Xa together activate thrombin well

20
Q

what are the pathways to activate factor X

A
  • extrinsic Xase enzyme
  • intrinsic Xase enzyme
  • thrombin through positive feedback
21
Q

what is extrinsic Xase

A

tissue factor + factor VIIa

22
Q

what is intrinsic Xase

A

factor VIIIa + IXa

23
Q

which factors does thrombin activate

A
  • factor VIII

- factor V

24
Q

where are clotting factors made

A

liver

25
Q

what is vitamin K

A
  • a class of related fat-soluble vitamins
  • is required to synthesise prothrombin (II), VII, IX and X
  • essential for gamma carboxylation of clotting enzymes
26
Q

what is plasmin

A
  • lyses fibrin to stop or destroy clots
  • starts as inactive plasminogen (made by liver)
  • requires tissue plasminogen activator on endothelial cells to mature
27
Q

what is protein C

A
  • coagulation inhibitor
  • works with cofactor protein S to inactivate Va
  • inactivates factor VIIIa
  • activated on surface of endothelial cells
28
Q

what is antithrombin II

A
  • works with heparin

- blocks activity of thrombin, Xa and IXa

29
Q

what reverses the effects of heparin

A

protamine sulfate

30
Q

what is haemophilia A caused by

A
  • congenital lack of factor VIII

- X-linked so only males have symptoms

31
Q

what is haemophilia B caused by

A
  • genetic defect in factor IX

- also called christmas disease

32
Q

what are symptoms of haemophilia A and B

A
  • affects larger blood vessels in joints and muscles

- wounds that bleed for days

33
Q

what are pharmalogical controls of blood clotting

A
  • anti-platelet agents generally for arterial disease
  • anti-coagulants generally for venous disease
  • fibrinolytics generally to dissolve fibrin in arterial disease
34
Q

what is aspirin

A
  • anti-platelet agent
  • blocks formation of thromboxane A2 in platelets
  • lengthens bleeding time without lengthening coagulation time
  • used after myocardial infarction
35
Q

what are anticoagulant drugs and how do they work

A
  • heparins inhibit factor Xa
  • dabigatran inhibits thrombin
  • rivaroxaban inhibits factor Xa
  • warfarin is a vitamin K antagonist
36
Q

examples of fibrinolytics

A
  • tissue plasminogen activator
  • streptokinase
  • urokinase

103 Theme 2 (8 decks)

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