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FA2 Clinical Pathology > Lecture 7 9/10/24 > Flashcards

Lecture 7 9/10/24 Flashcards

1
Q

What is primary hemostasis?

A

-formation of platelet plug
-adequate to stop bleeding from small vessels

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2
Q

What is secondary hemostasis?

A

-formation of stable fibrin clot
-necessary to stop bleeding from medium to large vessels

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3
Q

What is fibrinolysis?

A

breakdown of clots, necessary to restore non-turbulent blood flow in the vessel

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4
Q

What is clot inhibition?

A

prevention of unnecessary or excessive clot formation

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5
Q

What is the vascular phase of hemostasis?

A

reflex vasoconstriction that helps to prevent excessive blood loss

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6
Q

What is the platelet phase of hemostasis?

A

-von Willebrand Factor binds subendothelial collagen
-GPIb platelet adhesion molecule binds vWF
-platelets are activated, promoting platelets to bind to other platelets using fibrinogen as adhesive

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7
Q

What are the characteristics of secondary hemostasis?

A

-requires enzymes and cofactors, Ca++, and platelets
-traditional coagulation cascade occurs in vitro and is used to interpret hemostatic tests
-cell-based coagulation occurs in vivo and highlights of cell contributions

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8
Q

How does the intrinsic pathway differ from the extrinsic pathway?

A

extrinsic pathway initiates hemostasis, while intrinsic pathway amplifies hemostasis

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9
Q

How does in vitro hemostasis differ from in vivo hemostasis?

A

in vitro hemostasis requires Factor 12 for the initiation of hemostasis; in vivo, Factor 12 is not needed

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10
Q

Why is thrombin known as the master regulator of hemostasis?

A

thrombin has multiple roles throughout the different stages of hemostasis

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11
Q

What is the goal of the initial activation of the coagulation cascade?

A

to produce a small amount of thrombin that can be used to activate the intrinsic pathway and amplify thrombin production

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12
Q

Which steps of hemostasis occur on the fibroblast?

A

-exposed tissue factor and factor 7 start a reaction that leads to a small amount of thrombin production
-thrombin initiates the conversion of factor 11 into factor 11a
-factor 11a travels to platelet plug

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13
Q

Which steps of hemostasis occur on the platelet plug?

A

-intrinsic pathway activation leads to lots of thrombin formation
-thrombin converts fibrinogen in the platelet plug to soluble fibrin
-thrombin activates Factor 13 which converts soluble fibrin to crosslinked fibrin

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13
Q

What occurs during fibrinolysis?

A

fibrinogen, fibrin, and crosslinked fibrin are broken down into fragments

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14
Q

Which fragments are produced from fibrinogen, fibrin, and crosslinked fibrin?

A

-fibrinogen: FDPs
-fibrin: FDPs
-crosslinked fibrin: FDPs and D-dimers

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15
Q

What is plasminogen converted into?

A

plasmin

16
Q

What is the role of plasmin?

A

convert fibrinogen/fibrin into its components

17
Q

What is the importance of clot inhibition?

A

inadequate clot inhibition can lead to thrombosis

18
Q

What are the characteristics of antithrombin?

A

-most clinically relevant clot inhibitor
-accounts for most of the anticoagulant activity in blood
-consumed as it inactivates thrombin
-small protein; can be lost in some conditions

19
Q

What are the characteristics of the buccal mucosal bleeding time test?

A

-small cut of standard size and depth
-tests primary hemostasis only
-insensitive and difficult to standardize

20
Q

Which conditions are disorders of primary hemostasis?

A

-thrombocytopenia: not enough platelets
-thrombopathia: platelets not working
-von Willebrand disease

21
Q

What two things can lead to an inaccurate platelet count on automated CBC?

A

-sample handling concerns
-platelet clumping

22
Q

What is the potential significance of an increased MPV/mean platelet volume?

A

-increased thrombopoiesis in marrow
-platelet activation or clumping

23
Q

What are the characteristics of vWF antigen testing?

A

-evaluates concentration of vWF protein in plasma
-reported as a percentage compared to normal plasma pool

24
Q

What are the requirements for activated clotting time/ACT testing?

A

-special tube with activator of the intrinsic coagulation pathway
-patient platelets

25
Q

What are the potential causes of prolonged ACT?

A

-severe defects in intrinsic and/or common pathway
-very severe thrombocytopenia

26
Q

What are the requirements for partial thromboplastin time/PTT?

A

-coagulation analyzer that adds in Factor 12 activator
-patient plasma from blue top citrate tube

27
Q

What causes a prolonged PTT?

A

defects of intrinsic and/or common pathway

28
Q

What are the requirements for prothrombin time/PT?

A

-coagulation analyzer that adds in tissue factor activator
-patient plasma from blue top citrate tube

29
Q

What causes a prolonged PT?

A

defects of extrinsic and/or common pathway

30
Q

How does ACT compare to PTT?

A

-both evaluate intrinsic and common pathways
-PTT requires a specific analyzer while ACT requires a specific collection tube
-ACT requires platelets while PTT does not
-ACT is less sensitive than PTT

31
Q

What are the methods for measuring fibrinogen concentration?

A

-thrombin clot time (increased time = decreased fibrinogen)
-Clauss fibrinogen method

32
Q

What are the requirements for measuring fibrinogen concentration?

A

-coagulation analyzer
-patient plasma from blue top citrate tube

33
Q

Which condition is most commonly evaluated for when measuring fibrinogen conc.?

A

hypofibrinogenemia

34
Q

What are the characteristics of D-dimers?

A

-produced when plasmin degrades crosslinked fibrin
-measured to detect fibrinolysis
-measured in an immunoassay

35
Q

What are the characteristics of antithrombin measurement?

A

-requires coagulation analyzer and patient plasma from a blue top citrate tube
-reported as percentage compared to normal plasma pool

36
Q

Which processes lead to excessive bleeding when they are disordered?

A

-primary hemostasis
-secondary hemostasis/coagulation

37
Q

Which processes lead to thrombosis when they are disordered?

A

-fibrinolysis
-clot inhibition

FA2 Clinical Pathology (21 decks)

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