Primary Haemostasis

Question 1

How are platelets formed

Answer 1

Fragmentation of megakaryocytes

Question 2

What is the name of the process by which platelets are formed

Answer 2

Endoreduplication

Question 3

What 2 substances control endoreduplication

Answer 3

Thrombopoietin

Colony stimulating factors

Question 4

How long does endoreduplication last

Answer 4

10 days in in humans

Question 5

True or false, platelets are nucleated biconvex discs

Answer 5

False, they are non nucleated

Question 6

Where do the platelets remain for the duration of the their lifetime

Answer 6

Intravascular space

Question 7

How long is the lifetime of platelets

Answer 7

8-10 days

Question 8

What functions do platelets have

Answer 8

Adhesive and contractile functions

Question 9

What are the growth phases of platelets

Answer 9

Stem cell, multipotent progenitor cell, commited megakaryocyte, immature megakaryocyte, mature megakaryocyte, platelets

Question 10

What is the main hematopoietic growth factor that regulates endoreduplication

Answer 10

Thrombopoietin

Question 11

Where is thrombopoietin produced

Answer 11

Liver and kidney

Question 12

What does the hormone thrombopoietin stimulate

Answer 12

Production and differentiation of megakaryocytes

Question 13

What are the specific antigens on platelets called ?

Answer 13

HPA

Question 14

What is the name of the three granules in platelets

Answer 14

Alpha, dense, lysosomes

Question 15

What are the names of the content in dense granules

Answer 15

ADP/ATP
Calcium
Serotonin

Question 16

What are the functions of the Dense contents

Answer 16

ADP/ATP- PLT agonist
Calcium- Regulates PLT activation
Serotonin- Promotes Vasoconstriction

Question 17

What is the function of the the lysosomes contents

Answer 17

Proteolytic, hydrolytic enzymes - digest vessel wall matrix and debris

Question 18

What are the functions of the alpha content

Answer 18

Thromboglobulin (beta- TG)- inhibit heparin; vessel repair
PF4- inhibit heparin
PDGF- vessel repair
Fibrinogen, Factors V and VIII- fibrin formation
vWF- PLT Adhesion
Plasminogen- Precursors of plasmin (fibrinolysis)
Alpha1-antiplasmin- Plasmin inhibitors
HMWK- contact activation; intrinsic coagulation path
Fibronectin- Promotes PLT spreading

Question 19

What is the normal platelet count cells/mm^3

Answer 19

100,000-400,000

Question 20

Term used to describe Platelet count <100,000

Answer 20

Thrombocytopenia

Question 21

What is the platelet count for mild thrombocytopenia

Answer 21

50,000-100,000

Question 22

What is the platelet count for severe thrombocytopenia

Answer 22

<50,000

Question 23

What substance inhibits platelet aggregation

Answer 23

Prostacyclin

Question 24

What process occurs when endothelium is ruptured

Answer 24

Haemostasis

Question 25

What are the steps in primary Haemostasis

Answer 25

Vasospasm Platelet plug formation Blood coagulation Fibrinolysis

Question 26

What is the role of the endothelial walls

Answer 26

Protecting blood from coagulation | Platelets from subendothelial aggregating substances

Question 27

What is he function of the tissue factor

Answer 27

Initiate coagulation

Question 28

What blood protein and sub endothelial connective tissue functions as a platelet subendothelium adhesion carriage of VIII

Answer 28

Collagen type 2 and 4 | Von Willebrand factor

Question 29

What subendothelial connective tissue and blood protein, functions to inhibit blood coagulation

Answer 29

Basement memebrane, microfibrils | Antithrombin 3 and protein C activation

Question 30

What are the steps in primary haemostasis after an injury

Answer 30

``` Vasoconstriction (immediately) Platelet adhesion (seconds) Platelet aggregation(minutes) ```

Question 31

What are the steps in secondary Haemostasis after an injury

Answer 31

Activation of coagulation factors | Formation of fibrin(minutes)

Question 32

What occurs in fibrinolysis

Answer 32

Activation of fibrinolysis (minutes) | Lysis of the clot (hours)

Question 33

What 3 substances functions in the adhesive property of platelets

Answer 33

GPl (collagen) GPIb VWF

Question 34

What two substances functions in stimulating the aggregation properties of platelets

Answer 34

ADP and thromboxane A2

Question 35

What occurs in the activation role of platelets

Answer 35

Change in shape (pseudopodia) | Secretions of contents like ADP, serotonin, fibrinogen thromboxane A2

Question 36

Synthesis of prostacyclin and thromboxane, are mediated by changes in the concentration of _________ in platelets via stimulation or inhibitor of the enzyme ___________.

Answer 36

Cyclic AMP | Adenylate cyclase

Question 37

High levels of cyclic AMP lead to ______ free calcium ion concentrations and prevent _______ and ______

Answer 37

Low | Aggregation and adhesion

Question 38

After aggregation, what occurs

Answer 38

Platelets rearrange themselves to reveal binding sites for coagulation protein

Question 39

In the platelet procoagulation action what two substances are formed

Answer 39

Factor Xa and thrombin

Question 40

What ion activated the conversion of prothrombin to thrombin

Answer 40

Ca2+