Haemostasis

Question 1

Which substances are involved in clotting?

Answer 1

Platelets
vWF
Coagulation factors

Question 2

Which substances help to keep the clot confined to the site of injury?

Answer 2

Natural anticoagulants

Question 3

Which system removes the clot?

Answer 3

Fibrinolytic system

Question 4

In normal blood flow, does anything stick to the walls of vessels?

Answer 4

No

Question 5

How are platelets and coagulation factors activated?

Answer 5

Receive signals due to:
Abnormal surface
Physiological activator

Question 6

What is the role of platelets in haemostasis?

Answer 6

Adhere
Activation
Aggregation
Provide phospholipid surface for coagulation

Question 7

What is primary haemostasis?

Answer 7

Formation of a platelet plug

Question 8

What is secondary haemostasis?

Answer 8

Formation of a fibrin mesh

Question 9

What are the steps involved in primary haemostasis?

Answer 9

Vasoconstriction

Platelet adhesion

Question 10

Which substances normally block platelets from sticking to endothelium?

Answer 10

Nitric oxide

Prostacyclin

Question 11

What are nitric oxide and prostacyclin?

Answer 11

Vasodilators

Question 12

What is endothelin?

Answer 12

A vasoconstrictor

Question 13

What are the receptors on platelets involved in haemostasis?

Answer 13

Glycoprotein Ib

Glycoprotein IIbIIIa

Question 14

What is the molecule that provides a link between the site of injury and platelets?

Answer 14

von Willebrand factor

Question 15

Where is vWF normally found?

Answer 15

Circulates in blood but is also secreted at the site of injury

Question 16

What does vWF bind to at the site of injury?

Answer 16

Subendothelial collagen on one side and GpIb at the other

Question 17

What happens when the vWF binds to GpIb?

Answer 17

Changes shape of IIbIIIa so that it is now able to bind

Degranulation

Question 18

What is released by activated platelets into the blood?

Answer 18

Granules - alpha granule and dense granule

Thromboxane A2

Question 19

What does the alpha granule contain?

Answer 19

Fibrinogen

vWF

Question 20

What does the dense garnule (sac) contain?

Answer 20

Serotonin
ADP
Ca2+

Question 21

What is the function of serotonin released by platelets?

Answer 21

Smooth muscle constriction

Question 22

What happens to the ratio of NO/PC to endothelin at the site of injury?

Answer 22

NO/PC decreases so endothelin results in vasoconstriction

Question 23

What is the function of ADP released by platelets?

Answer 23

Activates more platelets

Question 24

What is the function of Ca released by platelets?

Answer 24

Required for secondary haemostasis

Question 25

What is the function of thromboxane A2 released by platelets?

Answer 25

Vasoconstriction | Activation and aggregation of platelets

Question 26

What mediates platelet aggregation?

Answer 26

Gp IIbIIIa

Question 27

Why is a fibrin mesh necessary?

Answer 27

Links up and aggregates on top of platelet plug to stabilise it

Question 28

What does fibrin circulate as?

Answer 28

Fibrinogen

Question 29

What are the ways in which the coagulation cascade can be triggered?

Answer 29

Intrinsic pathway - when subendothelial collagen is exposed to the blood Extrinsic pathway - protein secreted by endothelial cells whenever we have damage to the blood vessels from outside our bodies

Question 30

What is the protein secreted by endothelial cells whenever we have damage to the blood vessels from outside our bodies?

Answer 30

Tissue factor/thromboplastin

Question 31

What converts fibrinogen to fibrin?

Answer 31

Thrombin

Question 32

What is the inactive form of thrombin?

Answer 32

Prothrombin

Question 33

How does the coagulation cascade work?

Answer 33

Activated form of each factor activates the next

Question 34

Which factors are involved in the intrinsic pathway?

Answer 34

XII XI IX(+VIII) X(+V)

Question 35

Which factors are involved in the extrinsic pathway?

Answer 35

III(TF) VII

Question 36

Which factors are activated by thrombin?

Answer 36

5, 7, 9, 13

Question 37

What turns plasminogen to plasmin?

Answer 37

Thrombin

Question 38

What is the function of plasmin?

Answer 38

Acts of fibrin mesh to break them apart

Question 39

What stimulates anti-thrombin to decrease the production of thrombin from prothrombin and conversion of activated factor X to deactivated factor X

Answer 39

Thrombin

Question 40

Anticoagulation

Answer 40

Prevents clotting

Question 41

Thrombolysis

Answer 41

Breaks down clots

Question 42

What is factor V Leiden?

Answer 42

Factor V mutation | Makes factor V resistant to protein C

Question 43

What is protein S?

Answer 43

Protein C cofactor - helps protein C to work better

Question 44

What is the heparin-like molecule on the surface of endothelium?

Answer 44

Anti-thrombin III cogfactor

Question 45

What is the action of anti-thrombin (plus heparin-like cofactor)?

Answer 45

Interact to inactivate thrombin and factor X

Question 46

What is the function of a thrombomodulin/thrombin complex?

Answer 46

Activation of protein C

Question 47

What are the vitamin K dependent factors?

Answer 47

II VII IX X

Question 48

What is the function of vitamin K for certain factors?

Answer 48

Adds carboxyl groups whichc is important for enzyme activity

Question 49

What are the fat soluble vitamins?

Answer 49

A, D, E, K

Question 50

How are the vitamin K dependent factors measured?

Answer 50

PT/APTT/INR

Question 51

Where are factors made?

Answer 51

In the liver

Question 52

How does warfarin work?

Answer 52

Works on vitamin K dependent factors

Question 53

How do DOACs work?

Answer 53

Inhibit thrombin etc

Question 54

What prolongs PT?

Answer 54

Decreased level of vitamin K dependent factors Liver disease (especially cholestasis) Warfarin Rarely inherited deficiencies in factors 2, 7, 9 or 10 DIC/DOACs (but APTT will also be prolonged)

Question 55

How does liver disease affect vitamin K dependent factors?

Answer 55

Produced in the liver | Fat soluble so bile production has an effect

Question 56

What is cholestasis?

Answer 56

A decrease in bile flow due to impaired secretion by hepatocytes or to obstruction of bile flow through intra-or extrahepatic bile ducts, therefore any condition in which substances normally excreted into bile are retained

Question 57

What prolongs APTT?

Answer 57

``` Haemophilia A/B vWD (decrease in factor VIII) Unfractionated heparin (not LMWH) DIC DOACs ```

Question 58

APTT

Answer 58

Activated partial prothrombin time

Question 59

What is the cofactor for factor VIII?

Answer 59

von Willebrand factor

Question 60

What is used to measure patients on warfarin?

Answer 60

INR

Question 61

What aere the causes of DIC?

Answer 61

Coagulation is strongly triggered so factors are used up more quickly Any condition with increased production of TF

Question 62

Which tissues contain a lot of TF and what associated conditions result in DIC?

Answer 62

``` Brain - brain trauma Bones - multiple fractures Placenta - obstetric emergency Infection - monocytes express TF Cancer cells express TF (more chronic) ```

Question 63

How are vitamin K dependent factors activated?

Answer 63

Carboxylated by vitamin K

Question 64

Which factors are inhibited by heparin?

Answer 64

2, 7, 9, 10