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Haematology SOH > Haemostasis > Flashcards

Haemostasis Flashcards

1
Q

Definition

A

The arrest of bleeding and the maintenance of vascular patency

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2
Q

What does primary haemostats involve?

A

Formation of the platelet plug

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3
Q

If someone gets a minor injury, e.g. paper cut, primary homeostasis and secondary homeostasis is usually activated. True or false?

A

False

- only primary homeostasis

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4
Q

What does secondary homeostasis involve?

A

Formation of the fibrin clot

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5
Q

What is the function of fibrin clot formation in secondary homeostasis?

A

Protien mesh that holds the platelets in a secure position so that they cannot be washed away by blood flowing through the body

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6
Q

Describe fibrinolysis

A

When a blood clot forms, the body wants to break it down to allow blood flow and restore patency

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7
Q

What b/d plasminogen -> plasmin?

A

tPA

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8
Q

What can be used as a measure of fibrinolysis?

A

D dimers

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9
Q

What happens in primary homeostasis

A
  1. Endothelial (vessel wall) damage
  2. Collagen is exposed
    - release of vWF (which platelets have receptors for)
    - platelets are attracted to the area, they come and stick to the collagen (platelet adhesion)
  3. Secretion of various chemicals from platelets
    - leads to aggregation of the platelets at the site of injury
  4. Activation
    - when platelets stick to each other, they change shape
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10
Q

Screening test for primary homeostasis

A

Platelet count

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11
Q

Where does secondary haemostasis occur?

A

On the surface of the platelet plug that has formed in primary haemostasis

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12
Q

The function of secondary homeostasis is to secure the platelet plug in place?

A

YEs

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13
Q

Platelets in the platelet plug are full of ?

A

Phospholipid

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14
Q

Clotting factors have a positive/negative charge?

A

Negative

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15
Q

Where are clotting factors usually made?

A

In the liver (mainly in hepatocytes)

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16
Q

Secondary homeostasis - activation of clotting factors - initiation

A

Endothelial injury -> Tissue factor exposed.

This recruits factor VII and activates it (VIIa)

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17
Q

Secondary homeostasis - activation of clotting factors - TF/VIIa complex goes on to activate

A

Factor V and X

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18
Q

Secondary homeostasis - activation of clotting factors - which clotting factors cause prothrombin -> thrombin

A

Factor Va and Xa

19
Q

Secondary homeostasis - activation of clotting factors - activation of thrombin

A

Factor IIa

20
Q

Secondary homeostasis - activation of clotting factors - activation of thrombin activates which 2 clotting factors

A

VIIIa and IXa

21
Q

VIIIa and IXa allow more of ___ and ___ to be activated

A

Va and Xa

22
Q

What is fibrinogen activated by?

A

Thrombin

23
Q

Secondary homeostasis - activation of clotting factors - activation of fibrin

A

Factor Ia

24
Q

name 2 screening tests for secondary homeostasis

A

Prothrombin time (PT)

Activates partial thromboplastin time (APTT)

25
Q

Prothrombin time (PT) - which clotting factors does it measure

A 
VII 
V
X 
Prothrombin (II) 
Fibrinogen (I)
26
Q

Prothrombin time (PT) - which colour of lid is on the sample bottle?

A

Light blue

27
Q

Prothrombin time (PT) - what does it measure

A

The amount of time it takes to form a fibrin clot from liquid blood

28
Q

What is a normal PT

A

12-16 seconds

29
Q

When may PT be abnormal

A

Abnormality of clotting factors - VII, V, X, prothrombin, fibrinogen

Use of oral anti-coagulants

30
Q

APTT - what does it measure

A

The amount of time it takes to form a thrombin clot

31
Q

what is a normal APTT

A

26-37 seconds

32
Q

Prolonged APTT
Normal PT
If this picture occurs, which clotting factors are affected?

A

VIIIa

IXa

33
Q

Name 4 naturally occurring anticoagulants

A

Factor V Leiden
Antithrombin
Protein C
Protein S

34
Q

The action of antithrombin is greatly potentiated by _____

A

Heparin

35
Q

how does antithrombin switch off blood clotting

A

Binds to an inactivates thrombin formation

Switches off Xa formation

36
Q

Activated protein C switches off which 2 clotting factors

A

V
VIII

This reduces further thrombin generation

37
Q

What is protein S

A

A co-factor for protein C

38
Q

If you have factor V leiden gene then you cannot make normal factor V. True or false?

A

False

- can make normal factor V but it means that factor V is less efficiently switched off by protein C+S

39
Q

What are the 4 clotting factors

A

II, VII, IX, X

40
Q

For clotting factors to be activated, they require ?

A

Vitamin K

41
Q

What does vitamin K do to clotting factors?

A

Carboxylates clotting factors

42
Q

What is the investigation for the extrinsic pathway

A

PT

43
Q

What is the investigation for the intrinsic pathway

A

APTT

Haematology SOH (22 decks)

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