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Hematology > Episode 5 Hemostasis > Flashcards

Episode 5 Hemostasis Flashcards

1
Q

What is the name of the megakaryocyte stem cell?

A

Hemocytoblast -> Megakaryocyte -> Promegakaryocyte -> Megakaryocyte -> Thrombocyte

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2
Q

What is the vasocontrictive phase triggered by?

A

Direct injury itself, SympatheticNS

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3
Q

During platelet plug formation, what do platelets stick to?

A

Exposed collagen

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4
Q

Platelets stick to exposed collagen thru what receptors?

A

GP 1a receptors

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5
Q

Where is von Willebrand’s Factor (vWF) made?

A

They leak out from damaged endothelial cells of blood vessels

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6
Q

Where is vWF found?

A

Plasma, platelets, and walls of blood vessels.

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7
Q

What do GP1b receptors bind to?

A

vWF

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8
Q

What happens to platelets during adhesion?

A

Platelets will undergo major structural changes and adhesion triggers the secretion of multiple factors from the platelets

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9
Q

What three major chemicals are released from platelets that adhere to damaged endothelial walls?

A

ADP, TXA2 (Thromboxane A2 or TA2), and Serotonin (5-HT)

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10
Q

What becomes of the platelet granules when they degranulate?

A

They become the released factors of ADP, TXA2, and 5-HT

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11
Q

What do the released factors from platelets do?

A

They bind other platelets to stick together and form an aggregate

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12
Q

Which platelet receptor participates in aggregation and binding of fibrinogen?

A

GP2b/3a

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13
Q

When does the coagulation phase (blood clotting) occur?

A

It reinforces a platelet plug or stops bleeding when a platelet plug fails

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14
Q

Roughly how many clotting factors are out there?

A

20

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15
Q

Where are most of the clotting factors present and in what form?

A

Present in circulation as inactive proteins (zymogens)

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16
Q

What are inactive clotting factors usually activated by?

A

Other clotting factors

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17
Q

Which clotting factors are Vitamin K dependent?

A

II, VII, IX, X

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18
Q

What is the difference b/w extrinsic and intrinsic blood clotting pathways?

A

Extrinsic are initiated outside the blood (via tissue thromboplastin). Intrinsic are initiated within the blood by platelets

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19
Q

Which clotting factors participate in the extrinsic mechanism?

A

III, IV, V, VII

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20
Q

What clotting factor is possessed by all cells?

A

Thromboplastin (factor III), leak out of damaged tissue and finds its way into blood

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21
Q

Is factor III normally in blood?

A

No, it leaks out from damaged cells

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22
Q

When factor III (thromboplastin) and IV (Ca++) get into the blood, what factor do they activate?

A

Factor VII

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23
Q

Factor VII along with factor V will activate what factor?

A

Factor X

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24
Q

T/F the extrinsic and intrinsic clotting pathways are initiated simultaneously.

A

T

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25
Q

Which factor do chemicals released from platelets activate?

A

Factor XII

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26
Q

What does factor XII activate?

A

Factor XI

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27
Q

What does factor XI activate?

A

IX

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28
Q

What does factor IX along with Ca++ and PF3 activate?

A

Factor VIII

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29
Q

What cofactors does factor IX need to activate factor VIII?

A

Ca++ and PF3

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30
Q

What does factor VIII activate?

A

Factor X

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31
Q

T/F both factor VII and factor VIII activate factor X individually

A

T

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32
Q

What does factor X (along with III, IV, V, and PF3) activate?

A

Prothrombin activator

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33
Q

What does prothrombin activator do?

A

Converts Prothrombin (factor II) into thrombin

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34
Q

What does Thrombin do?

A

Converts fibrinogen (factor 1) into fibrin

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35
Q

What does factor XIII and Ca++ (factor IV) do?

A

Allow fibrin to stick together in forming a fibrin polymer

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36
Q

What are three “Natural” anticoagulants?

A

Thrombomodulin, Antithrombin, Heparin cofactor II

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37
Q

What does thrombomodulin bind to?

A

Thrombin

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38
Q

What doe the thrombomodulin-thrombin complex activate?

A

Protein C (just a plasma protein floating around w/ all of our other proteins!)

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39
Q

What is the cofactor of Protein C required to inactivate Factors V and VIII?

A

Protein S

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40
Q

Where is thrombomodulin made?

A

On the surface of the endothelial cells

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41
Q

Where is antithrombin made?

A

Liver

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42
Q

What does antithrombin inhibit?

A

Factor X and thrombin

43
Q

Where is heparin cofactor II made?

A

in the liver

44
Q

What does heparin cofactor II inhibit?

A

thrombin

45
Q

Which two anticoagulant inhibit thrombin?

A

Antithrombin and heparin cofactor II

46
Q

Which enzyme converts plasminogen to plasmin?

A

tissue plasminogen activator (tPA)

47
Q

Where is plasminogen made?

A

Liver

48
Q

What does plasmin do?

A

Dissolves plasmin - it is a fibrinolytic

49
Q

What cells release tPA?

A

damaged endothelial cells

50
Q

What happens to tPA?

A

gets trapped in a clot

51
Q

How is a clot broken down?

A

tPA and plasminogen were both trapped in clot as it formed, after several days tPA will slowly activate plasminogen

52
Q

What are fibrinolysis inhibitors?

A

a check and balance on the tPA to prevent prolonged or unwanted degradation of fibrinogen

53
Q

What are two tPA inhibitors?

A

Plasminogen activator inhibitor 1 and Plasminogen activator inhibitor 2

54
Q

Which two fibrinolysis inhibitors act directly on plasmin to prevent it from dissolving fibrin?

A

alpha-2-antiplasmin and alpha-2-macroglobulin

55
Q

What are petechia?

A

pinpoint hemorrhages on skin and mucous membranes

56
Q

How does the CBC test help to assess the clotting system?

A

Platelet count

57
Q

For coagulation tests, blood is collected in tubes containing what?

A

Sodium citrate

58
Q

Citrate will bind to what?

A

Calcium

59
Q

What does the normal functioning of the coagulation cascade require?

A

Calcium

60
Q

What color tube contains sodium citrate?

A

Blue

61
Q

What does the prothrombin time (PT) test do?

A

It assess the extrinsic pathway of the blood clotting cascade

62
Q

Why is calcium added to plasma in the PT test?

A

To replace the calcium removed by citrate

63
Q

Why is brain thromboplastin added to plasma in the PT test?

A

To substitute for tissue factor

64
Q

How long does does clotting normally take?

A

12-15 seconds

65
Q

What is the test clotting time compared to?

A

A standard normal control in a ratio

66
Q

What was the International Normalized Ratio (INR) devised for?

A

To standardize test results between different batches and manufacturers of tissue factor

67
Q

What is tissue factor?

A

Key initiator of the coagulation cascade, formerly known as thromboplastin, AKA factor III

68
Q

What is the ISI?

A

A fudge factor to come up with a standardized INR

69
Q

What does INR tell you?

A

How well your blood clots

70
Q

The INR is always used in pts taking which drug?

A

Warfarin (coumadin)

71
Q

What is the INR number needed for basic blood-thinning needs?

A

2.0 to 3.0

72
Q

What does an INR of 2.0 to 3.0 mean?

A

This persons blood usually takes two to three times longer to form a clot

73
Q

If someone is taking coumadin and their INR is 6.2, what does that mean?

A

They are taking too much coumadin, and have an increased risk for spontaneous bleeding

74
Q

If someone is taking coumadin and their INR is 1.0, what does that mean?

A

They are not taking enough coumadin! Their risk for forming spontaneous clots

75
Q

What is the difference between the Prothrombin Time (PT) test and the Activated Partial Thromboplastin Time (APTT) test?

A

PT assess extrinsic pathway and APTT assesses intrinsic clotting pathway

76
Q

In an APTT test why is calcium added?

A

To replace the calcium removed by citrate

77
Q

In an APTT test why are kaolin and phospholipids added?

A

To substitute for contact factor, its going to contact FXII and activate it, it is replacing the natural chemicals released from platelets

78
Q

How long does clotting normally take in the APTT test?

A

25-36 seconds

79
Q

What is APTT most often used for clinically to monitor?

A

To monitor heparin therapy

80
Q

When is heparin used vs coumadin?

A

Heparin is used on an inpatient basis, while coumadin is used on an outpatient basis

81
Q

What does UFH stand for?

A

Unfractionated heparin

82
Q

For someone taking heparin what is a good APTT value?

A

2-2.5 times that of normal value (so that would be clotting taking 72 seconds to clot, for example, instead of the normal 36

83
Q

What is the Thrombin Clotting Time (TT) test used to assess?

A

Used to assess the common pathway

84
Q

What do you have to add for the TT test?

A

Calcium (to replace that removed by citrate) and thrombin (to substitute for the products of the intrinsic and extrinsic pathways)

85
Q

When is the TT test used?

A

When PT and APPT test is prolonged, particularly when abnormal fibrinogen level or function is considered

86
Q

What are coagulation factor assays used for?

A

to determine actual deficiencies of specific clotting factors (eg FVII, FIX, etc)

87
Q

Hemophelia A is a mutation in the gene for what factor?

A

FVIII

88
Q

What would be the result of an APPT test on someone who has Hemophilia A? PT test?

A

Prolonged APPT. PT would be normal

89
Q

What percentage of Hemophilia A has no family history?

A

30% (majority are inherited, however)

90
Q

Where are the most serious sites of bleeding in Hemophiliacs?

A

Joint capsules, skeletal muscles, GI tract, and Brain

91
Q

What is the main cause of pain in joints of hemophiliacs?

A

Enzymes that breakdown blood in the joints also degrade the bone

92
Q

Which factor is given to pts that experience repeated and painful bleeds into their joints?

A

FIV (calcium)

93
Q

what is the most common bleeding disorder?

A

Von Willebrand’s Disease (vWD)

94
Q

What are the two major roles of vWF?

A

mediating platelet adhesion and stabilizing factor VIII

95
Q

Where is bleeding typically seen in vWD?

A

skin and mucous membranes

96
Q

Which test result is similar and which one is different for Hemophilia A and vWD patients?

A

Both pts would have prolonged APPT and reduced FVIII clotting activity (intrinsic pathway). However, PT is only prolonged in vWD patients. In Hemophilia A PT is normal

97
Q

Why is the PT test in vWD pts prolonged?

A

Failure of platelet-vessel wall interaction

98
Q

What are the common causes of thrombocytopenia?

A

Impaired production of platelets (drug induced or bone marrow failure). Increased destruction of platelets (idiopathic thrombocytopenic purpura (ITP))

99
Q

What is ITP?

A

autoimmune response to platelets, which are removed prematurely by the reticuloendothelial system

100
Q

What are some examples of inherited thrombophilias?

A

Protein C deficiency
Protein S deficiency
Activated Protein C Resistance (poor response by FV, FV is not inactivated by Protein C like it should be)
Antithrombin III deficiency

101
Q

What is Hemophilia B a mutation in?

A

Mutation in FIX

102
Q

What are the APPT and PT test results for Hemophilia A and B?

A

APPT is prolonged; PT is normal. These are in contrast to vWD which has a prolonged PT as well

103
Q

How can FV Leiden be treated?

A

Give normal FV. The FV the person has does not re

Hematology (6 decks)

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