Health and Disease Week 5

Question 2

What is blood production controlled by?

Answer 2

multiple protein cytokines (release by WB cells) and growth factors

Question 3

What detects blood vessel damage?

Answer 3

platelet surface receptors

Question 4

What do platelets secrete? Why?

Answer 4

soluble factors to activate neighbouring platelets

Question 5

What is required for a clotting cascade?

Answer 5

multiple blood proteins

Question 6

What does thrombopoietin do?

Answer 6

regulate production of platelets

Question 7

What does erythropoietin do?

Answer 7

regulate production of erythrocytes

Question 8

What are the major precursors of platelets?

Answer 8

megakaryocytes

Question 9

What kind of cells give rise to haematopoietic precursors of blood cells?

Answer 9

pluripotent stem cells

Question 10

What creates a bruise?

Answer 10

when blood vessel endotheliums become damaged and blood leaks into surrouding tissues

Question 11

What is the scientific name for blood clotting?

Answer 11

haemostasis

Question 12

What 2 stages can clotting be broken down into?

Answer 12

1. primary haemostasis
2. secondary haemostasis

Question 13

What happens in primary haemostasis?

Answer 13

platelets form a plug and are attracted to site of damage

Question 14

What happens in secondary haemostasis?

Answer 14

a blood clotting mechanism is used to transform and stabilise the weak platelet plug into a clot by a fibrin network

Question 15

What is the 1st step of platelet plug formation?

Answer 15

adhesion

Question 16

What are the steps of adhesion in platelet plug formation?

Answer 16

1. damage to endothelium cells exposes subendothelial tissue which is made up of collagen fibres
2. collagen activates platelets and they adhere to these collagen fibres via an intermediate protein called von Willebrand factor (vWF)
3. platelets binding to collagen causes a release of ADP and serotonin from their secretory vesicles, resulting in more platelet activation

Question 17

What is the 2nd step of platelet plug formation?

Answer 17

platelet activation

Question 18

What are the steps of platelet activation?

Answer 18

1. release of ADP and serotonin from vesicles
2. this causes change in shape and surface protein expression of platelets

Question 19

What is the 3rd step of platelet plug formation?

Answer 19

platelet aggregation

Question 20

What are the steps of platelet aggregation?

Answer 20

1. platelets adhere to each other to form a plug
2. synthesis and release of thromboxane A2 from arachidonic acid enhances more activation and aggregation

Question 21

What stabilises the platelet plug?

Answer 21

fibrinogen bridges that form when receptors in the platelet surface become exposed during activation

Question 22

What causes contraction of the plug?

Answer 22

actin and myosin

Question 23

What do healthy endothelial cells do?

Answer 23

synthesis and release of Prostacyclin (PGI2) and nitric oxide, which both inhibit platelet activation

Question 24

What is the scientific name for a clot?

Answer 24

a thrombus

Question 25

What is a clot?

Answer 25

the transformation of blood into a gel consisting of fibrin polymers that occurs around the platelet plug

Question 26

What does vessel damage activate?

Answer 26

a cascade of enzyme that results in the activation of an enzyme called thrombin

Question 27

What does the enzyme thrombin do?

Answer 27

cleaves a protein called fibrinogen into fibrin molecules that create the fibrin network

Question 28

Sequence of events

Answer 28

clotting factors -> prothrombin -> thrombin -> fibrinogen -> fibrin -> blood clot

Question 29

What are the overall steps of blood clotting?

Answer 29

1. damage to blood vessel lining triggers the release of clotting factors
2. formation of the platelet plug and vasoconstriction limits blood flow
3. development of the clot and fibrin strands adhere to form an insoluble clot

Question 30

How is thrombin activated?

Answer 30

activated from prothrombin which then cleaves fibrinogen to fibrin (which is stabilised by activation of factor 8 by thrombin)

Question 31

What are the steps in activating the clotting cascade for the extrinsic pathway?

Answer 31

1. initiated by a tissue factor, not blood protein, on the outside of plasma membrane of cells in the sub-endothelial tissue
2. tissue factors activates factor 7 and they both activate factor 10
3. generates small amounts of thrombin
4. thrombin then feeds back onto the intrinsic pathway to activate components and generate more thrombin

Question 32

What are the steps of beginning the enzyme cascade in the intrinsic pathway of the clotting cascade?

Answer 32

1. clotting factor 12 is activated by contact with collagen

Question 33

What is the role of the liver in blood clotting?

Answer 33

• produces many clotting factors
• produces bile salts which are required for absorption of vitamin K needed for production of prothrombin

Question 34

What does thrombin do?

Answer 34

it is an enzyme that recruits the intrinsic pathway and activates factor 5 and activates platelets

Question 35

How does the protease activated receptor on platelets activate them?

Answer 35

1. the enzyme thrombin binds and cleaves the thrombin receptor at a specific site on the N terminus on a platelet
2. the cleaved N terminus can then bind and activate the receptor on the platelet

Question 36

What are examples of clotting disorders?

Answer 36

damage to endothelium (myocardial infarction), clots (deep vein thrombosis), clotting disorders (haemophilia)