Blood (HLB)

Question 1

What is haemostasis?

Answer 1

Process of stopping bleeding

Question 2

What are the stages of haemostasis?

Answer 2

1) Vasoconstriction
2). Primary haemostasis = formation of platelet plug
3). Secondary haemostasis = reinforcement of platelet plug

Question 3

What is the name of the process which produces platelets?

What is the receptor involved in this?

What cell do platelets originate from?

Answer 3

Thrombopoiesis

TPO

Megakaryocytes

Question 4

What is the name of the process which produces RBCs?

Which receptor is involved in this?

Answer 4

Erythropoeisis

EPO

Question 5

What causes vasoconstriction when blood vessels are injured?

Answer 5

Endothelial cells produces endothelin - this causes regional arterioles to constrict.

Endothelial cells that are injured also produce thromboxane A2 and 5HT - these cause nearby smooth muscle to contact, also increasing vasoconstriction.

Question 6

What are the three steps of platelet plug formation?

Answer 6

Platelets adhere to a BV wall
Platelets are activated
Platelets aggregate

Question 7

How to platelets bind to an injured blood vessel wall?

Answer 7

Beneath the wall lies collagen which has been exposed. VWF can bind to this collagen - and then it attaches to platelets via the GP1b receptor

Question 8

When platelets are activated, what do they release?

Answer 8

Granules of ADP, thromboxane A2 and 5HT

Question 9

How does platelet aggregation occur in an injury?

Answer 9

ADP & Thromboxane A2 are released from bound, activated platelets. These attract other passing platelets to the site of injury.

Platelets can then bind to each other via GP2b3a receptors - fibrinogen binds them together.

Question 10

Which disease can cause a defect in the receptor GP1b on platelets - causing haemophilia.

Answer 10

Bernard-Soulier syndrome

Question 11

Which disease can cause a decrease in levels of VWF?

Answer 11

VW disease

Question 12

What is thrombocytopenia?

Answer 12

A decreased amount of platelets in the blood - can cause inability to clot properly.

Question 13

Which disease can affect the platelet receptor GP2b3a - thereby reducing coagulation?

Answer 13

Glanzmann’s thrombasthenia

Question 14

What are the three pathways of the coagulation cascade?

Answer 14

Intrinsic
Extrinsic
Common

Question 15

Which factors are involved in the intrinsic pathway?

Answer 15

12, 11, 9, & 8

Question 16

Which factors are involved in the extrinsic pathway?

Answer 16

7 & 3

Question 17

What is the result of both of the intrinsic and extrinsic pathways?

Answer 17

They convert Factor X to Xa

Factor Xa + Va + Platelet Factor 3 + Ca convert Prothrombin to Thrombin (FII)

Thrombin converts Fibrinogen –> Fibrin (F I). Fibrin jellies the blood and forms a mesh over the clot.

Thrombin + FXIII + Ca = F XIIIa = cross links fibrin strands making the mesh stronger.

Question 18

Which factors require Vitamin K?

Answer 18

7, 9 & 10

Question 19

Which drug is a vitamin K inhibitor?

Answer 19

Warfarin

Question 20

How affect does liver disease have on Vitamin K?

Answer 20

Decreases its absorption

Question 21

How is excessive clot formation controlled by the body?

Answer 21

Plasminogen activator is also secreted from damaged cells.

This converts Plasminogen to plasmin.

Plasmin degrades fibrin fibres and limits growth of thrombi.

Question 22

What is naturally secreted by endothelial cells of blood vessels to prevent unnecessary blood clotting?

What other mechanisms do these cells have to stop blood clotting?

Answer 22

PGI2 and NO

They also have heparin sulphate - which binds to Anti-thrombin and activates it - in turn this inactivates 2, 9 & 10

Finally they have thrombomodulin - binds thrombin and activates Protein C. Protein C degrades 5 & 8.

Question 23

Which deficiency would you have with
- Haemophilia A
- Haemophilia B

Answer 23

A - F8 deficiency
B - F9 deficiency

Question 24

What are the natural anticoagulants in the body?

Answer 24

Protein C

Protein S

Anti-Thrombin

Question 25

How does anti-thrombin work as a natural anticoagulant?

Answer 25

It inhibits 2 + 7 = 9… 10, 11,12

Question 26

How does heparin work?

Answer 26

It enhances the effect of anti-thrombin - heparin binds and activates it.

The APTTR is derived from the activated partial thromboplastin time (APTT) of the patient and the midpoint of the APTT reference range.