Haemostasis

Question 1

Definition

Answer 1

The arrest of bleeding and the maintenance of vascular patency

Question 2

What does primary haemostats involve?

Answer 2

Formation of the platelet plug

Question 3

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

Answer 3

False

- only primary homeostasis

Question 4

What does secondary homeostasis involve?

Answer 4

Formation of the fibrin clot

Question 5

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

Answer 5

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

Question 6

Describe fibrinolysis

Answer 6

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

Question 7

What b/d plasminogen -> plasmin?

Answer 7

tPA

Question 8

What can be used as a measure of fibrinolysis?

Answer 8

D dimers

Question 9

What happens in primary homeostasis

Answer 9

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

Question 10

Screening test for primary homeostasis

Answer 10

Platelet count

Question 11

Where does secondary haemostasis occur?

Answer 11

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

Question 12

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

Answer 12

YEs

Question 13

Platelets in the platelet plug are full of ?

Answer 13

Phospholipid

Question 14

Clotting factors have a positive/negative charge?

Answer 14

Negative

Question 15

Where are clotting factors usually made?

Answer 15

In the liver (mainly in hepatocytes)

Question 16

Secondary homeostasis - activation of clotting factors - initiation

Answer 16

Endothelial injury -> Tissue factor exposed.

This recruits factor VII and activates it (VIIa)

Question 17

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

Answer 17

Factor V and X

Question 18

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

Answer 18

Factor Va and Xa

Question 19

Secondary homeostasis - activation of clotting factors - activation of thrombin

Answer 19

Factor IIa

Question 20

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

Answer 20

VIIIa and IXa

Question 21

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

Answer 21

Va and Xa

Question 22

What is fibrinogen activated by?

Answer 22

Thrombin

Question 23

Secondary homeostasis - activation of clotting factors - activation of fibrin

Answer 23

Factor Ia

Question 24

name 2 screening tests for secondary homeostasis

Answer 24

Prothrombin time (PT)

Activates partial thromboplastin time (APTT)

Question 25

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

Answer 25

``` VII V X Prothrombin (II) Fibrinogen (I) ```

Question 26

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

Answer 26

Light blue

Question 27

Prothrombin time (PT) - what does it measure

Answer 27

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

Question 28

What is a normal PT

Answer 28

12-16 seconds

Question 29

When may PT be abnormal

Answer 29

Abnormality of clotting factors - VII, V, X, prothrombin, fibrinogen Use of oral anti-coagulants

Question 30

APTT - what does it measure

Answer 30

The amount of time it takes to form a thrombin clot

Question 31

what is a normal APTT

Answer 31

26-37 seconds

Question 32

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

Answer 32

VIIIa | IXa

Question 33

Name 4 naturally occurring anticoagulants

Answer 33

Factor V Leiden Antithrombin Protein C Protein S

Question 34

The action of antithrombin is greatly potentiated by _____

Answer 34

Heparin

Question 35

how does antithrombin switch off blood clotting

Answer 35

Binds to an inactivates thrombin formation Switches off Xa formation

Question 36

Activated protein C switches off which 2 clotting factors

Answer 36

V VIII This reduces further thrombin generation

Question 37

What is protein S

Answer 37

A co-factor for protein C

Question 38

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

Answer 38

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

Question 39

What are the 4 clotting factors

Answer 39

II, VII, IX, X

Question 40

For clotting factors to be activated, they require ?

Answer 40

Vitamin K

Question 41

What does vitamin K do to clotting factors?

Answer 41

Carboxylates clotting factors

Question 42

What is the investigation for the extrinsic pathway

Answer 42

PT

Question 43

What is the investigation for the intrinsic pathway

Answer 43

APTT