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Hematology I > Module 3 > Flashcards

Module 3 Flashcards

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1
Q

Five major components of hemostasis

A 
Vascular component
Platelet component
Coagulation system
Fibrinolytic system
Natural anticoagulants (antifactors) and inhibitors
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2
Q

What do endothelial cells secrete to maintain thromboresistance?

A

Heparin sulphate
Prostacyclin
Nitrous oxide/Endothelium derived relaxing factor (EDRF)

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3
Q

Where is heparin sulphate secreted and what does it do?

A

Secreted by normal, intact vascular endothelial cells

Inhibits coagulation

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4
Q

Where is prostacyclin secreted and what does it do?

A

Secreted by normal, intact vascular endothelial cells

Inhibits platelet adhesion and aggregation

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5
Q

Where is endothelium derived relaxing factor (EDRF) secreted and what does it do?

A

Secreted by normal, intact vascular endothelial cells

Relaxes smooth muscles in the subendothelial area and prevents vasoconstriction

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6
Q

Vascular patency

A

The prevention of blood cells from leaking out of circulation while still allowing diapedesis of motile cells

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7
Q

2 types of vasoconstriction

A

Muscular - immediate

Humoral - delayed

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8
Q

2 most important substances released by damaged vessels and injured cells

A

Tissue thromboplastin

Tissue plasminogen activator (tPA)

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9
Q

Exposure of subendothelium to plasma results in:

A

Adhesion of platelets to the subendothelium

Some contact activation of the intrinsic coagulation system

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10
Q

Tissue thromboplastin

A

Coagulation factor III
A lipoprotein released from injured cells that acts as a coenzyme with factor VII to activate the extrinsic coagulation system of reactions in the plasma

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11
Q

Tissue plasminogen activator (tPA)

A

Activates the fibrinolytic system in the blood plasma

Some is released by the injury; more in secreted later to dissolve the clot as healing takes place

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12
Q

Substance that inhibits the enzyme cyclooxygenase

A

ASA - acetyl salicylic acid

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13
Q

Which coagulation factor is not found in blood plasma?

A

Factor III

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14
Q

The role of vitamin K in hemostasis

A

Vitamin K is a coenzyme required for gamma-carboxylation of the PT group factors - without the final carboxylation, they are inactive

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15
Q

What does coagulation factor III activate?

A

Factor VII, then VII and III together activate factors X, IX and XI

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16
Q

Production of fibrinopeptides A and B indicates what?

A

Coagulation; that is, thrombin converts to fibrinogen into fibrin monomer and fibrinopeptides A and B

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17
Q

How does fragment X inhibit thrombin?

A

Fragment X neutralizes thrombin by binding to it

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18
Q

What is meant by natural inhibitors and anticoagulants?

A

Substances normally present in the blood that will inhibit or neutralize activated components of hemostasis that escape from the site of an injury

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19
Q

What is a soluble fibrin monomer complex?

A

The combination of a fibrin monomer and fragment Y

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20
Q

Closure time

A

A screening test for platelet ability to adhere and aggregate under conditions simulating that of capillary flow

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21
Q

Platelet maturation series

A

Megakaryoblast
Megakaryocyte
Thrombocytes

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22
Q

Platelet aggregation requires:

A

ADP and thrombin

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23
Q

Canalicular system in platelets

A

Extensive canal system from the interior to the exterior of the platelet
Carries granular contents to the surface during release reactions

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24
Q

Dense bodies (delta granules) in platelets

A

2-10 per platelet
Rich in: serotonin, vasoactive catecholamines (epinephrine, norepinephrine and dopamine), nucleotides (AMP, ADP, ATP), calcium, pyrophosphate

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25
Alpha (translucent) granules in platelets
50-80 per platelet Gives platelets their granular appearance when stained Contain: PF3, fibrinogen, thrombospondin, PF4
26
Dense tubular system in platelets
Layers of internal membranes Store calcium for release as needed Important in platelet retraction and prostaglandin synthesis
27
Lifespan of platelets in circulation
8-10 days
28
How is thrombopoiesis different from production of other blood cells?
Megakaryocytes get larger as they mature | No cellular division occurs, endomitosis (nuclear division) instead
29
3 zones in a platelet
Peripheral zone Sol-gel zone Organelle zone
30
Peripheral zone of a platelet
Plasma membrane and glycocalyx | Important in adhesion and aggregation of platelets
31
Sol-gel zone of a platelet
Cytoskeleton Contains contractile proteins like actomyosin and thrombosthenin Important in platelet retraction and shape changes
32
PF3
Platelet phospholipid Accelerates coagulation reactions by participating in the activation of coagulation factor X and prothrombin Acts as an organizational surface to bring required factors into close proximity and facilitate reaction
33
PF4
Anti-heparin factor | A glycoprotein that inhibits the action of heparin
34
How does heparin work in anticoagulation?
Helps to decrease the activity of thrombin
35
Sequence of events that occurs in platelets after injury to a vessel
``` Platelet adhesion Platelet aggregation Primary (reversible) aggregation Secondary (irreversible) aggregation Platelet retraction ```
36
Hemostatic functions of platelets
Involvement in plug formation The physical filling of holes in vessel walls Includes adhesion, aggregation, and retraction
37
Thromboplastic functions of platelets
Platelets release chemicals that reinforce vasoconstriction, aggregation, and coagulation reactions and that promote growth and healing
38
Calcium is required to activate which coagulation factors?
Factors VII, IX, X, II and XIII
39
Why don't we test for factor XIII in PT/APTT testing?
Its function is to stabilize the clot, activated/used after the clot has formed
40
What does thrombin do?
1. Catalyzes the formation of fibrin from fibrinogen 2. Activates factors V into Va and VIII into VIIIa 3. Along with ADP, induces and reinforces secondary platelet aggregation - viscous metamorphosis and the release reaction 4. Activates factor XIII, which stabilizes the clot 5. Weakly catalyzes the conversion of plasminogen into plasmin (activates the fibrinolytic system) 6. Binds with thrombomodulin in the membrane of endothelial cells and this complex activates Protein C, which destroys factors V and VIII and inhibits tPA activator 7. Weakly activates factor VII along with Xa and IXa 8. Enhances the activation of factor XI by the VIIa/III complex
41
Platelet adhesion requires
GP1b and VWF
42
Primary aggregation
Reversible Platelets first form a loose aggregate that plugs up the injury temporarily Requires ADP, GPIIbIIIa, Ca2+, fibrinogen
43
Secondary aggregation
Irreversible Requires ADP and thrombin Induces prostaglandin synthesis of platelets from primary aggregation - viscous metamorphosis and release reaction
44
Thromboxane A2 function
1. Causes release of calcium 2. Lowers cAMP levels in platelets (causing release reaction to occur) 3. Powerful vasoconstrictor
45
How does thromboxane A2 lower cAMP levels in the platelets?
By inhibiting the enzyme adenylcylclase, which converts ATP into cAMP
46
cAMP concentration is regulated by which 2 enzymes?
Adenyl cyclase and phosphodiesterase
47
Effect of Aspirin on hemostasis
Inhibits cyclooxygenase, therefore decreasing the production of thromboxane A2
48
Screening tests for platelet component
Platelet count Closure time Bleeding time Capillary fragility
49
Platelet count, closure time, bleeding time, and capillary fragility are what kind of tests
Screening tests for platelet component
50
Specific tests for platelet function
``` Measure the ability of platelets to adhere, aggregate and retract Platelet adhesion tests Platelet aggregation tests Prothrombin consumption time PF3 availability Clot retraction ```
51
Platelet adhesion tests, platelet aggregation tests, prothrombin consumption time, PF3 availability, and clot retraction are what kind of tests
Specific tests for platelet function
52
Specific tests to determine the cause of thrombocytopenia
Bone marrow examination Tests for anti-platelet antibody Platelet survival studies
53
What activates plasminogen (fibrinolysis)?
tPA (tissue plasminogen activators) Thrombin (direct but weak activator) XIIa, HMWK, and PK
54
Actions of plasmin
Digests and destroys the structure/activity of fibrinogen and fibrin, producing fdp and FDP Destroys factors V, VIII, IX, XI Activates complement Enhances/amplifies factor XII and PK
55
Roles of FDP and fdp in hemostasis
Inhibit thrombin Inhibit fibrin polymerization (clot formation) Increase vascular permeability
56
Reference range for platelet count
150-400 x 10^9/L
57
cAMP
Cyclic adenosine monophosphate | Inhibits the aggregation of platelets, ie. the less cAMP in the cell, the more aggregation there is
58
PT
Prothrombin time Evaluates the extrinsic pathway Measures factors VII, X, V, II, and I
59
APTT
Activated partial thromboplastin time Evaluates the intrinsic pathway Measures factors HMWK, PK, XII, XI, IX, VIII, X, V, II, and I
60
What does thrombin bind with to activate protein C?
Thrombomodulin (secreted by endothelial cells)
61
Actions of protein C
Destroys factors V and VIII | Inhibits tPA inhibitor
62
Test for FDP
Fibrinogen assay
63
FDP and fdp actions
Inhibit thrombin Inhibit fibrin polymerization (clot formation) Increase vascular permeability
64
How is Thromboxane A2 produced during secondary platelet aggregation?
ADP and thrombin complex activates enzymes that break down platelet membrane phospholipids Arachidonic acid is released Cyclooxygenase turns arachidonic acid into PG H2 TxA2 synthetase turns PG H2 into Thromboxane A2
65
Factors in the contact group
XII, XI, PK, HMWK Not consumed during coagulation Not dependent on vitamin K
66
Factors in the fibrinogen group
I, V, VIII, XIII | Consumed during coagulation
67
Factors in the prothrombin group
II, VII, IX, X Vitamin K dependent Not consumed during coagulation (except partially II)
68
Coagulation factors that are synthesized in the liver
I, II, V, VII, IX, X
69
Cofactor to antithrombin III
Heparin
70
Vitamin K dependent coagulation factors
II, VII, IX, X
71
Coagulation factors produced by hepatic cells
II, VII, IX, X, V, I

Hematology I (4 decks)

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