Blood clotting

Question 1

How many haemorrhage classes are there?

Answer 1

4

Question 2

What is the volume of class 1 haemorrhage and what is the effect?

Answer 2

Up to 15% blood volume

No medical intervention needed

Question 3

What is the blood volume of class 2 haemorrhage and what are the effect?

Answer 3

15 - 30% blood volume
Rapid heart rate, blood pressure variances, pale and cool skin
Saline solution given

Question 4

What is the blood volume of class 3 haemorrhage and what are the effects?

Answer 4

30 - 40% blood volume
BP drops, HR increases, brain function decreased
Saline solution and blood transfusion

Question 5

What is the blood volume of a class 4 haemorrhage and what are the effects?

Answer 5

> 40% blood volume lost
Dead ting
Resuscitation required

Question 6

What is haemostasis? (3)

Answer 6

Vascular spasm (reduces flow through vessel)
Formation of a platelet plug
Formation of a blood clot

Question 7

What is a vascular spasm? (3)

Answer 7

Damage to the blood vessel
Increases resistance to blood flow
Damage activates sympathetic nervous system - vasoconstriction

Question 8

What are the cellular components of human blood? (8)

Answer 8

Erythrocytes
Leukocytes
Neutrophils
Eosinphils
Basophils
Monocytes
Lymphocytes
Platelets

Question 9

What are platelets and what do they contain? (3)

Answer 9

Colourless cell fragments that break off from the megakaryocytes

Mitochondria, SER, cytoplasmic granules, NO nucleus
100,000 per ml

Question 10

What is the structural difference between an active and inactive platelet?

Answer 10

Active - spiky outer surface and adherence to each other

Inactive - small cell fragments circular

Question 11

What is the von Willibrand factor?

Answer 11

vWf is secreted by megakaryocytes, platelets and endothelial cells - bind to exposed collagen

Question 12

How is the platelet plug formed?

Answer 12

vWf binds to exposed collagen
Platelets bind to vWf and this triggers adherence
Platelets secrete: Serotonin, Epinephrine, ADP

Question 13

What are the 3 things platelets secrete once bound to vWf and what do they do?

Answer 13

Serotonin
Epinephrine
ADP - stimulates thromboxane A2 - TXA2 to promote further platelets

Question 14

What stops clots blocking the whole blood vessel? (2) And what starts it?

Answer 14

Prostacyclin
Nitric acid

Thromboxane A2 (TXA2) causes the platelet plug formation!

Question 15

What are the 7 main factors involved in platelet function and what are their roles?

Answer 15

Collagen - binds to platelets to begin plug
von Willibrand factor - links platelets to collagen
Serotonin - platelet aggregation
Adenosine diphosphate - platelet aggregation
Platelet-activating factor - platelet aggregation
Thromboxane A2 - platelet aggregation
Platelet-derived growth factor - Promotes healing

Question 16

What is a fibrin clot? (4)

Answer 16

Fibrinogen is essential for clot formation
Fibrin clot formation is secondary to platelet plug
Requires activated platelets and their secretary products
All triggered by the coagulation cascade

Question 17

What are the 2 pathways that begin the coagulation cascade?

Answer 17

Intrinsic and extrinsic

Question 18

Describe the intrinsic pathway: (3)

Answer 18

XII –> Active XII
Active XII + XI + thrombin + Ca2+ –> Active XI
Active XI + IX + Ca2+ –> Active IX

Question 19

Describe the extrinsic pathway:

Answer 19

VII + active X –> Active VII

Question 20

Describe the common pathway that leads after intrinsic/extrinsic? (4)

Answer 20

X + Ca2+ –> Active X
Active X + prothrombin + Ca2+ –> Thrombin
Thrombin + Fibrinogen –> Fibrin
Fibrin + Active XIII + Ca2+ —-> Cross-linked fibrin

Question 21

What are the 8 factors involved in coagulation?

Answer 21

Collagen - starts intrinsic pathway
vWf - regulates level of factor VIII
Tissue factor - starts extrinsic pathway
Prothrombin and thrombin - fibrin production
Fibrinogen and fiblin - Insoluble fibers to stabilize platelet plug
Fibrin-stabilising factor - cross links for stable mesh
Ca2+ - required for most steps
Vitamin K - needed for synthesis of factors

Question 22

How is a clot removed? (2)2

Answer 22

When clot formation is activated, so is plasmin

Plasmin gets trapped in the clot and slowly dissolves it

Question 23

What prevents coagulation from continuing until the vessel is fully blocked? (3)

Answer 23

Inhibition of platelet adhesion
Inhibition of fibrin production
Endothelial cells release anticoagulants (heparin and antithrombin 3)

Question 24

What 2 molecules do endothelial cells release?

Answer 24

Heparin

Antithrombin 3

Question 25

What does warfarin do?

Answer 25

Removes calcium and Active X

Question 26

What are 3 anticoagulant drugs and why are they prescribed?

Answer 26

They are prescribed to stop blood clots forming in major organs

Coumarin anticoaggulants (warfarin) - blocks vitamin K
Ca2+ removal
Acetylsalicyclic acid (aspirin) - inhibits COX enzymes thromboxane A2

Question 27

What is the role of aspirin in blocking platelet plug formation?

Answer 27

Blocks TXA2 production when platelets coagulate

Question 28

What can cause coagulation disorders? (6)

Answer 28

Liver disease
Hepatitis
Cirrhosis
Vitamin K deficiency
Haemophilia
Low blood platelets

Question 29

What is haemophilia? (2)

Answer 29

Factor VIII deficiency

Recessive sex linked