Haemostasis:

Question 1

What is haemostasis?

Answer 1

Prevents and stops bleeding

Question 2

How quickly after injury does hemostasis occur?

Answer 2

Seconds to hours

Question 3

What are the three main processes in hemostasis?

Answer 3

Vasoconstriction, platelet aggregation, leucocyte migration

Question 4

What happens when there is too little hemostasis?

Answer 4

Excessive bleeding, clotting defects and platelet deficiency

Question 5

What happens if there is too much hemostasis?

Answer 5

Thrombus formation, atherosclerosis, septicemic shock

Question 6

How many platelets are in a ml of blood?

Answer 6

250 million

Question 7

What is thrombocytopenia?

Answer 7

Struggle with blood clotting

Question 8

What happens to the structure of a platelet when it is activated?

Answer 8

Morphological change - changes from a smooth to rough surface with extensions due to rearrangement of actin and myosin

Question 9

How are platelets activated?

Answer 9

• Platelets adhere to damaged collagen
• Binding sites include involvement of von Willebrand factor (vWF)
• vWF released from endothelial cells and present in plasma
• Platelets become activated

Question 10

How is platelet activation an example of positive feedback?

Answer 10

Activated platelets release biochemicals into area for increased vasoconstriction, which results in more collagen being exposed and more platelets being activated

Question 11

What does ADP do in platelet plug formation?

Answer 11

Makes platelets sticky

Question 12

What does serotonin do in platelet plug formation?

Answer 12

Activates vasoconstriction

Question 13

What does thromboxane A2 do in platelet plug formation?

Answer 13

It is a prostaglandin - vasoconstrictor and activates

Question 14

How does a platelet plug form?

Answer 14

• Adhesion, activation, aggregation
• ADP makes platelets sticky
• Serotonin activates vasoconstriction
• Thromboxane A2 is a prostaglandin - vasoconstricts and activates
• Platelet adhesion activates platelets (morphological and biological change)

Question 15

What is a platelet plug?

Answer 15

Cell fragments of megakaryotes present in the blood with no nucleus/organelles/DNA/proteins

Question 16

What are the two pathways in the coagulation cascade?

Answer 16

Intrinsic and extrinsic

Question 17

When is the intrinsic pathway triggered?

Answer 17

When blood in cells is exposed to collagen

Question 18

Why must venepuncture test tubes be coated with anti-coagulant?

Answer 18

To stop initiation of the intrinsic pathway

Question 19

Where does the extrinsic pathway occur?

Answer 19

Tissues

Question 20

What is factor 13 activated by?

Answer 20

Thrombin

Question 21

What happens during the intrinsic pathway?

Answer 21

Co-factors 12, 11 and 9 are activated which converts 10 to its active form

Question 22

What does thrombin do?

Answer 22

Converts fibrinogen to fibrin to form a mesh

Question 23

Do RBCs contribute to the hemostasis process?

Answer 23

No

Question 24

Where is fibrinogen produced?

Answer 24

Liver

Question 25

Describe the process of the final common pathway in the coagulation cascade

Answer 25

Prothrombin activator converts prothrombin to thrombin Reaction requires calcium Thrombin converts fibrinogen into fibrin This forms cross-linked fibrin clot

Question 26

What happens during the intrinsic pathway?

Answer 26

Activated by contact with a damaged surface | factor XII - factor XI - factor IX (+factor VIII and vWF)

Question 27

What happens during the extrinsic pathway?

Answer 27

Activated by release fo tissue factors | Factor VII - common pathway

Question 28

What does prostacyclin do?

Answer 28

From intact endothelium, inhibits platelet adhesion and aggregation

Question 29

What does nitro oxide do?

Answer 29

From intact endothelium inhibits platelet adhesion

Question 30

How does the liver assist with clotting?

Answer 30

Synthesises clotting factors and bile salts

Question 31

What do bile salts do?

Answer 31

Increase rate of uptake of vitamin K from GI tract and move it to blood

Question 32

What does warfarin do?

Answer 32

Vit K antagonist | Anticoagulant

Question 33

How is a clot removed?

Answer 33

- Cell growth and cell division repairs damaged vessel - Clot retracts and dissolves - Plasmin (an enzyme) trapped in the clot acts on fibrin to break it into soluble fragments - Plasmin takes around a week to act

Question 34

How is plasmin made?

Answer 34

Plasminogen reacts with TPA

Question 35

How does the endothelium prevent clot formation?

Answer 35

Intact it separates collagen, tissue factors and vWF

Question 36

How does glycocalyx prevent clot formation?

Answer 36

Inhibits adhesion of platelets

Question 37

How do prostacyclin and nitric oxide prevent clot formation?

Answer 37

Inhibits platelet activation and aggregation

Question 38

How do CD39 and ecto-ADPases prevent clot formation?

Answer 38

Metabolize ADP

Question 39

How does TPA prevent clot formation?

Answer 39

Dissolves fibrin

Question 40

How does heparin sulphate prevent clot formation?

Answer 40

Co-factor for antithrombin

Question 41

Why is antithrombin an anti-coagulant?

Answer 41

Inactivates thrombin | Inactivates factor Xa and IXa

Question 42

Which factors do coumarin drugs impact?

Answer 42

II, VII, IX and X

Question 43

What is a thromboembolism?

Answer 43

Abnormal clot formation

Question 44

What is a thrombus?

Answer 44

Clot attached to vessel

Question 45

What is an emboli?

Answer 45

Free-floating clots

Question 46

Examples of anti platelet drugs

Answer 46

Aspirin, clopidogrel

Question 47

Examples of anticoagulant drugs

Answer 47

Warfarin, heparin

Question 48

Examples of fibrinolytic drugs

Answer 48

Urokinase, streptokinase, genetically engineered tissue plasminogen activator (t-PA)

Question 49

Why should aspirin not be taken before surgery?

Answer 49

Reduces platelets binding to sub-endothelial components Impairs platelet aggregation Prolongs bleeding

Question 50

Where is heparin used?

Answer 50

Catheters, dialysis, heart-lung machines

Question 51

Examples of calcium ion reducers

Answer 51

EDTA, citrate, oxalate

Question 52

What do siliconised containers do?

Answer 52

Reduce platelet activation

Question 53

Processes inside haemostasis

Answer 53

Vasoconstriction Platelet aggregation Leucocyte migration

Question 54

Processes inside inflammation

Answer 54

Early = neutrophil, late = macrophage Chemoattractant release phagocytosis

Question 55

Processes inside proliferation

Answer 55

Collagen and ECM synthesis Angiogenesis Fibroblast proliferation Granulation tissue formation

Question 56

Processes inside remodelling

Answer 56

Epithelialisation ECM remodelling Increase in wound strength