Platelets - formation, action and inhibition

Question 1

a thrombus

Answer 1

clot blocking a blood vessel

Question 2

when collagen is exposed due to endothelial damage platelets stick to it when this happens platelets get activated and release chemical that calls on more platelets - what is this molecule

Answer 2

thromboxane A2 (TxA2)

Haemostasis is a protective mechanism whereby blood flow is arrested by localised vasoconstriction and through the initiation of a blood clot through the clotting cascade. Effective haemostasis will thus help prevent significant blood loss through breaches in blood vessels due to damage in the blood vessel wall

Question 3

ontop of platelets fibrin proteins sticks platelets together forming the clot
the fibrin will trap what cells in it

Answer 3

RBC - THIS PROCESS REPEATS CAUSING A CLOT OR A THROMBUS

Question 4

cox inhtiobrs stop thrombus forming by stopping TxA2 what is an example of this

Answer 4

aspirin - platelets won’t stick together and clot won’t be formed
side effect is accessive bleeding

Question 5

what cells are your smallest blood cells at 2-4micrometres and are colourless

Answer 5

platelets

Question 6

platelet granules are unique among secretory vesicles in both content and their life cycle there are two types what are they

Answer 6

dense granules and alpha granules

Question 7

what are dense granules

darker

Answer 7

these contain high concentrations of low molecular weight compounds that potentiate platelet activation ( contains phospholipids, triglycerides, cholesterol, ATP, ADP , serotonin( 5HT which obtain while passing through GIT))

Question 8

what are alpha granules

Answer 8

concentrate large polypeptides that contribute to both primary and secondary homeostasis containing secreted proteins such as clotting factors and PDGF

Question 9

normal platelet count

Answer 9

150000-400000 per mm^3

Question 10

life span of platelet

Answer 10

8-12 days average 10

Question 11

platelets are destroyed by tissue macrophages in the spleen

a bigger spleen ( splenomegaly ) reduced platelet count so removal of the spleen …( splenectomy- remove spleen)

Answer 11

increase platelet count

Question 12

where does thrombopoiesis occur

Answer 12

bone marrow

also lungs

haemocytoblast- magakaryoblast - promegakaryocte - megakaryocte - platelets

Question 13

what is the coagulation triad - the triangle of death

Answer 13

coagulation proteins ( hyper coagulation) 
platelts ( stasis of blood flow)
endothelium ( endothelia injury)

Question 14

the intrinsic pathway contains what factors

Answer 14

12,11,9,8

extrinsic is Tf and 7

Question 15

protein S acts where

Answer 15

factor 8

Question 16

protein c acts where

Answer 16

factor 5

dmaged blood vessel lead to release of clotting factors covering prothrombin to thrombin then fibrinogen to fibrin leading to development of a clot

Question 17

platet bound by the three receptors ……
platelet granules relates relaxing ADP, ATP and serotonin , causing additional platelet aggregation and activation. Phospholipase c is activated by platelet causing calcium release leading to phospholipase A2 activation leading to TXa production as well as platelet surface changing and activating thrombin all increasing platelet activation and aggregating

Answer 17

GP1b
GPV
GPIX

Question 18

Moa of clopidogrel - anti-platelet ( prevent heart attack and strokes)

Answer 18

selectively inhibits ADP binding to P2Y12 receptor on the platelet thereby inhabiting platelet aggregation - irreversible

Question 19

Moa of aspirin

Answer 19

blocks prostacyclin synthesis - non selective COX-1 inhibitor inhibiting platelet aggregation for about 7-10 days

Question 20

What is the clotting factor that activates platelets

Answer 20

vWF

Question 21

Which cytosolic component of platelets is responsible for ADP release?

Answer 21

dense granules

Question 22

How are platelets destroyed by the body after circulating for 8-12 days?

Answer 22

Phagocytosis by macrophages in the spleen

Question 23

Which cell is responsible for platelet production?

Answer 23

Megakaryoblasts

Question 24

The key function of platelet induced clotting is to…

1. …form a platelet plug
2. …inhibit Tissue Factor release
3. …promote fibrin formation
4. …prevent atherosclerosis

Answer 24

1 and 3

Question 25

The primary factors that propagate platelet clot formation are:

Answer 25

ADP and Thromboxane A2

Question 26

What is the precursor molecule to Thromboxane A2?

Answer 26

Prostaglandin H2

Question 27

What is the primary target of the drug Aspirin in order to prevent clot formation?

Answer 27

COX1

Question 28

What is the mechanism of action of the drug clopidogrel bisulphate?

Answer 28

ADP receptor antagonist