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Physiology 2 > Haemostasis and Clot Lysis > Flashcards

Haemostasis and Clot Lysis Flashcards

1
Q

What is haemostatis ?

A

Prevention of blood loss

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2
Q

What are the three phases of haemostasis?

A
  1. Vascular spasms
  2. Platelet plug formation
  3. Coagulation
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3
Q

What do vascular spams do?

A

Cause immediate vasoconstriction in response to injury which limits the blood flow therefore limits blood loss

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4
Q

What will damage to endothelium release and what does this cause?

A

Endothelin

Causes vasoconstriction

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5
Q

How is damage to the vascular smooth muscle mediated ?

A

Contraction of the smooth muscle cells

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6
Q

How are nervous reflexes mediated ?

A

Sympathetic NS

Sensory nerve fibres that detect pain

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7
Q

What causes vasoconstriction of the vascular smooth muscle during vascular spasms?

A
  1. Nervous reflexes
  2. Myogenic contraction
  3. Factors from damaged tissue and activated platelets e.g. endothelin, thromboxane A2, serotonin (5-HT)
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8
Q

What is exposed when a blood vessel wall is damaged?

A

~Collagen

~Tissue factor

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9
Q

What happens when collagen is exposed to blood?

A

— Platelets begin to adhere to the exposed collagen, activate and release chemicals called platelet factors
— Platelets aggregate into a loose platelet plug

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10
Q

How are platelets actives?

A

By contact with:

  1. Von Willebrand factor
  2. Thrombin
  3. Collagen
  4. A negatively charged surface
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11
Q

What produces von Willebrand factor and when is this production highest?

A

Endothelial cells

Damaged endothelial cells

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12
Q

Why is blood not stored in glass?

A

The platelets would become activated due to the negatively charged surface of the glass and would cause the blood to begin to clot

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13
Q

What do the spines of activated platelets allow them to do?

A
  1. To stick to each other

2. To stick to the damaged surface of the blood vessel

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14
Q

What are the normal features of the endothelial surface of a vessel wall?

A
  1. Smooth
  2. Has a glycocalyx
  3. Releases prostacyclin and NO
  4. Contains thromobomodulin
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15
Q

What forms a glycocalyx and what does it do?

A

Made up of mucopolysaccharides

It physically repels the platelets and clotting factors

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16
Q

Why do platelets not normally stick to the vessel wall?

A

As it has an endothelial surface

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17
Q

What do prostacyclin, NO and thrombomodulin do?

A

Prevent platelet activation

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18
Q

What do activated platelets release ?

A
  • ADP
  • Thromboxane A2
  • Serotonin
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19
Q

What type of feedback is platelet plug formation an example of?

A

Positive feedback

20
Q

What initiates the clotting cascade ?

A

Tissue factor

21
Q

What activates clotting factor XII and where are they activated ?

A

Platelets

Liver

22
Q

When do the extrinsic and intrinsic pathways finish ?

A

Clotting factor X

23
Q

Does clotting occur faster in the intrinsic of extrinsic pathway?

A

Extrinsic

24
Q

What is factor X critical in?

A

The conversion of prothrombin (II) to thrombin (II) through complexing with prothrombin activator

25
Q

What does thrombin convert?

A

Fibrinogen (I) to fibrin

26
Q

What actually forms the clot?

A

Fibrin

27
Q

What stabilises the fibrin mesh ?

A

Activated clotting factor XIII

28
Q

What activated factor XIII and where is it located ?

A

Thrombin

Surface of platelets

29
Q

What is serum?

A

Plasma - the clotting proteins

30
Q

Why do we store blood samples with citrate or EDTA?

A

Calcium ions are pro coagulants and these prevent the blood from clotting

31
Q

Why is vitamin K important in coagulation ?

A

—Many clotting factors produced by the liver are activated through vitamin K dependent reactions.

— Vitamin K is also necessary for the binding of Ca++ in many reactions

32
Q

How can warfarin act as an anti-coagulant ?

A

It prevents / inhibits the enzyme that normally causes activation of vitamin K from converting inactive vitamin K to active vitamin K

33
Q

Is vitamin K water or fat soluble ?

A

Fat soluble

34
Q

What are the fat soluble vitamins ?

A

A
D
E
K

35
Q

What releases heparin and what is it?

A

It is and anticoagulant released by mast cells and basophils

Heparin enhances the formation of anti thrombin III from the liver

36
Q

What does antithrombin III do?

A

Bind and inactivated thrombin

37
Q

How does aspirin work as an anti-coagulant ?

A

Inhibits the enzyme (cycle-oxygenate) that forms thromboxane A2

38
Q

What converts plasminogen to plasmin ?

A

Fibrin-specific plasminogen activators produced by endothelial cells

39
Q

What causes an increase in fibrin-specific plasminogen activators ?

A

Increase in thrombin in the blood (when there is a clot )

40
Q

What is plasmin?

A

A protease that breaks down the fibron clot

41
Q

What does bleeding time measure ?

A

Vascular spasms and platelet plug formation (phases one and two)

42
Q

What does a long bleeding time indicate ?

A

Problem with platelet function

43
Q

What does clotting time measure ?

A

Phase 3 - coagulation

44
Q

What is true name of a thrombus that pulls away from the vessel?

A

Embolism

45
Q

What can a clot cause?

A

Myocardial infarction
Stroke
Deep vein thrombosis
Pulmonary embolism

Physiology 2 (11 decks)

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