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Basic Haemotology (1204) > Primary Haemostasis > Flashcards

Primary Haemostasis Flashcards

1
Q

How are platelets formed

A

Fragmentation of megakaryocytes

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2
Q

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

A

Endoreduplication

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3
Q

What 2 substances control endoreduplication

A

Thrombopoietin

Colony stimulating factors

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4
Q

How long does endoreduplication last

A

10 days in in humans

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5
Q

True or false, platelets are nucleated biconvex discs

A

False, they are non nucleated

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6
Q

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

A

Intravascular space

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7
Q

How long is the lifetime of platelets

A

8-10 days

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8
Q

What functions do platelets have

A

Adhesive and contractile functions

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9
Q

What are the growth phases of platelets

A

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

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10
Q

What is the main hematopoietic growth factor that regulates endoreduplication

A

Thrombopoietin

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11
Q

Where is thrombopoietin produced

A

Liver and kidney

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12
Q

What does the hormone thrombopoietin stimulate

A

Production and differentiation of megakaryocytes

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13
Q

What are the specific antigens on platelets called ?

A

HPA

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14
Q

What is the name of the three granules in platelets

A

Alpha, dense, lysosomes

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15
Q

What are the names of the content in dense granules

A

ADP/ATP
Calcium
Serotonin

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16
Q

What are the functions of the Dense contents

A

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

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17
Q

What is the function of the the lysosomes contents

A

Proteolytic, hydrolytic enzymes - digest vessel wall matrix and debris

18
Q

What are the functions of the alpha content

A

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

19
Q

What is the normal platelet count cells/mm^3

A

100,000-400,000

20
Q

Term used to describe Platelet count <100,000

A

Thrombocytopenia

21
Q

What is the platelet count for mild thrombocytopenia

A

50,000-100,000

22
Q

What is the platelet count for severe thrombocytopenia

23
Q

What substance inhibits platelet aggregation

A

Prostacyclin

24
Q

What process occurs when endothelium is ruptured

A

Haemostasis

25
Q

What are the steps in primary Haemostasis

A

Vasospasm
Platelet plug formation
Blood coagulation
Fibrinolysis

26
Q

What is the role of the endothelial walls

A

Protecting blood from coagulation

Platelets from subendothelial aggregating substances

27
Q

What is he function of the tissue factor

A

Initiate coagulation

28
Q

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

A

Collagen type 2 and 4

Von Willebrand factor

29
Q

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

A

Basement memebrane, microfibrils

Antithrombin 3 and protein C activation

30
Q

What are the steps in primary haemostasis after an injury

A 
Vasoconstriction (immediately)
Platelet adhesion (seconds)
Platelet aggregation(minutes)
31
Q

What are the steps in secondary Haemostasis after an injury

A

Activation of coagulation factors

Formation of fibrin(minutes)

32
Q

What occurs in fibrinolysis

A

Activation of fibrinolysis (minutes)

Lysis of the clot (hours)

33
Q

What 3 substances functions in the adhesive property of platelets

A

GPl (collagen)
GPIb
VWF

34
Q

What two substances functions in stimulating the aggregation properties of platelets

A

ADP and thromboxane A2

35
Q

What occurs in the activation role of platelets

A

Change in shape (pseudopodia)

Secretions of contents like ADP, serotonin, fibrinogen thromboxane A2

36
Q

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

A

Cyclic AMP

Adenylate cyclase

37
Q

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

A

Low

Aggregation and adhesion

38
Q

After aggregation, what occurs

A

Platelets rearrange themselves to reveal binding sites for coagulation protein

39
Q

In the platelet procoagulation action what two substances are formed

A

Factor Xa and thrombin

40
Q

What ion activated the conversion of prothrombin to thrombin

Basic Haemotology (1204) (16 decks)

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