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Liz's Hemostasis/Coagulation > The Vascular System > Flashcards

The Vascular System Flashcards

1
Q

State 5 reasons why a thrombus does not normally form in intact vessels

A
  • Smooth surface
  • Prostacyclin
  • Heparan sulfate
  • Tissue factor pathway inhibitor (TFPI)
  • Thrombomodulin
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2
Q

Platelet activation inhibitor

A

Prostacyclin

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3
Q

Activates antithrombin

A

Heparan sulfate

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4
Q

Inactivates VIIa…controls TF/extrinsic pathway

A

Tissue factor pathway inhibitor (TFPI)

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5
Q

Activates protein C pathway

A

Thrombomodulin

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6
Q

State 4 procoagulant properties of the vascular intima that lend to thrombus formation during vascular damage

A
  • Vasoconstriction
  • Basement membrane exposes collagen
  • von Willebrand factor secreted
  • Tissue factor exposed
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7
Q

Necessary for platelets to adhere to subendothelial collagen in arterioles; (and eventual) platelet aggregation

A

von Willebrand factor secreted

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8
Q

Activates plasma coagulation system (Factor VII)

A

Tissue factor exposed

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9
Q

Thrombopoiesis

- List 4 stages of maturation

A
  • Megakaryoblast
  • Promegakaryocyte
  • Megakaryocyte
  • Platelets (thrombocytes)
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10
Q

Thrombopoiesis

- Morphology of megakaryoblast

A
  • Round nucleus; 2-6 nucleoli
  • Homogeneous chromatin, loosely organized
  • Basophilic cytoplasm
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11
Q

Thrombopoiesis

- Morphology of promegakaryocyte

A
  • Indented nucleus; variable nucleoli
  • Condensed chromatin
  • Basophilic cytoplasm
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12
Q

Thrombopoiesis

- Morphology of megakaryocyte

A
  • Nucleus, 2-32 lobes (8 most common)
  • Blue to pink cytoplasm, abundant
  • Reddish-blue granules
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13
Q

Thrombopoiesis

- Morphology of platelets (thrombocytes)

A
  • No nucleus
  • Light blue to colorless cytoplasm
  • Red to violet, abundant granules
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14
Q

Thrombopoiesis

- Site of platelet production

A
  • BM = medullary

- Lungs = extramedullary

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15
Q

Thrombopoiesis

- Regulatory mechanism

A

Growth factor, specifically thrombopoietin (hormone)

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16
Q

Morphology of normal platelet when stained w/ Wright’s stain

A
  • Chromomere aka granulomere
  • Hyalomere
  • Outside of platelets is light color and round
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17
Q

Two pools into which platelets are distributed

A
  • Circulatory (2/3)

- Splenic (1/3)

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18
Q

Average life span of the platelet

A

8-12 days

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19
Q

Four platelet functions

A
  • Source of PF3
  • Source of PF4
  • Maintain vessel integrity
  • Formation of platelet plug
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20
Q

Phospholipid found w/in platelet membrane is essential reaction site in the cascade

A

Source of PF3

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21
Q

Protein found in platelet’s alpha granules and is capable of neutralizing heparin

A

Source of PF4

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22
Q

What is the job of maintaining vessel integrity in platelets?

A

Platelets adhere to the subendothelial collagen, and fill in the gaps until new endothelial cells grow

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23
Q

List 4 causes of platelet activation caused by traumatic venipuncture and/or shaking of the sodium citrate tube

A
  • Subsequent release of PF4
  • PF4 will neutralize heparin in blood sample
  • Falsely shorten APPT
  • Potential for subsequent over anticoagulation of the patient
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24
Q

Formation of platelet plug

- Primary or secondary hemostasis?

A

Primary

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25
Q

Formation of platelet plug

- Short or long-term effect?

A

Short-term effect

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26
Q

Formation of platelet plug

- Two hemostatic systems involved w/ primary hemostasis

A
  • Vascular intimia

- Platelets

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27
Q

Formation of platelet plug

- List type of bleeding w/ disorder involved w/ primary hemostasis

A
  • Temporarily arrests bleeding

- Excessive bruising and mucocutaneous bleeding

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28
Q

Formation of platelet plug

- Type of diagnostic tests involved w/ primary hemostasis

A

Platelet tests

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29
Q

List 3 steps involved in primary hemostasis

A
  • Platelet adhesion
  • Platelet activation
  • Platelet aggregation
30
Q

Discuss platelet adhesion

A
  • Platelets first adhere to collagen
  • GPIb binds platelet to vWF (bridge)
  • GPIb/IX necessary to attach vWF bridge to subendothelium for platelet adhesion
31
Q

Discuss platelet activation

A

Platelets release procoagulant factors and synthesize prostaglandins to activate platelets

32
Q

Discuss platelet aggregation

A

Fibrinogen bridge and glycoprotein IIb/IIIa complex needed for platelets to attach to one another

33
Q

List 3 zones of platelet ultrastructure

A
  • Peripheral zone
  • Sol-gel zone
  • Organelle zone
34
Q

Functions as receptor and transmitter region as well as it’s essential for adhesion and aggregation

A

Peripheral zone

35
Q

Functions as cytoskeletal/contractile region

A

Sol-gel zone

36
Q

Functions as metabolic/organelle region and has two types of granules

A

Organelle zone

37
Q

Two types of granules in organelle zone

A

Alpha and dense bodies

38
Q

Differentiate quantitative vs. qualitative platelet testing

A 
Quantitative tests → NUMBERS
- Platelet count or slide estimate
Qualitative tests → FUNCTION
- Bleeding time
- Platelet function analyzer (PFA-100)
- Platelet aggregation
- Clot retraction
39
Q

Why is EDTA the anticoagulant of choice when performing electronic platelet counts?

A

Prevents clumping of platelets in most patients

40
Q

Anticoagulant used in automated platelet counts

A

EDTA

41
Q

What manual method is used for platelet counts?

A

Unopette method

42
Q

Anticoagulant used in Unopette method

A
  • Ammonium oxalate is used as the diluting fluid → lyses RBCs and platelets are mostly left behind
43
Q

Type of microscopy used in Unopette method

A

Phase microscopy retards wavelength and gives platelets a dark contrast → hard to see w/ a light microscope

44
Q

What should you do when you notice that no platelets are seen when performing a differential directly from a fingerstick?

A

Check the edges and tail on low power of the smear for platelet clumps

45
Q

Formula for estimated platelet count

A

Avg # of platelets x 20,000 (make sure you’re in OIF of 200 RBCs)

46
Q

Normal range for platelet counts

A

150-450 x 10^3/cumm; 150-450 x 10^9/L (in SI units)

47
Q

How will a hemolyzed sample affect an electronic platelet count?

A

↓ RBCs, hematocrit; H and H not in balance

48
Q

What should you do if you have a hemolyzed specimen?

A

Redraw the specimen or a manual Unopette method if ONLY a platelet count is ordered

49
Q

How do platelet clumps affect an electronic platelet count?

A

Causes falsely low results

50
Q

How can a valid count be obtained if platelet clumps exist?

A

Redraw specimen w/ sodium citrate and multiply the count by 1.1 for a valid count (b/c blood: anticoagulant ratio different)

51
Q

How do giant platelets affect an electronic platelet count?

A

Causes falsely low platelet counts

52
Q

How can a valid platelet count be obtained if giant platelets exist?

A

Performed manual Unopette method for a valid count b/c they’re greater than the threshold for the instrument

53
Q

How does platelet satellitism affect an electronic platelet count?

A

Causes falsely low platelet counts

54
Q

This test is defined as the time it takes for a standardized wound to stop bleeding and is concerned w/ both the # of platelets and their ability to form a viable platelet plug

A

Bleeding time (BT or TBT-Template Bleeding Time)

55
Q

Normal reference range for bleeding time

A

2-10 minutes

56
Q

6 clinical conditions that lead to an ↑ BT result

A
  • Thrombocytopenia
  • Aspirin
  • vWD
  • Bernard-Soulier Syndrome
  • Glanzmann’s thrombasthenia
  • Afribrinogenemia
57
Q

This is the most accurate test than the BT test where platelet adhesion and aggregation following vascular injury are stimulated in vitro

A

Platelet Function Analyzer (PFA-100)

58
Q

How is the PFA-100 performed?

A

Test cartridges are coated with platelet agonists and WB is aspirated through a microscopic cut in the cartilage membrane. The time required to occlude the aperature (“closure time”) is noted.

59
Q

What is considered the gold standard for platelet function testing?

A

Platelet aggregation

60
Q

How is platelet aggregation performed?

A

Platelet agonists/activating agents added to platelet rich plasma causing platelets to clump together, undergo shape change, and release granular contents. Clumping causes a clearing and patterns of light transmittance are charted and analyzed

61
Q

6 common agonists used in platelet aggregation studies

A
  • ADP (most common)
  • Arachidonic acid
  • Collagen
  • Epinephrine
  • Ristocetin
  • Thrombin
62
Q

This wave of aggregation is reversible and is a direct cause of adding ADP to PRP and causes platelet clumping

A

Primary wave

63
Q

This wave of aggregation is irreversible where alpha and dense bodies release factors

A

Secondary wave

64
Q

What does the ADP aggregation curve look like with aspirin ingestion?

A

Do not get to release factor so only primary curve is present

65
Q

What does the arachidonic acid curve look like with aspirin ingestion?

A

Absent platelet aggregation, no curve at all

66
Q

What does the ristocetin curve look like in vWD?

A

Flat line b/c you need vWF to have aggregation

67
Q

ONLY _____ aggregation has primary and secondary curves

A

ADP

68
Q

This drug inhibits both the release reaction and secondary wave of aggregation

A

Aspirin

69
Q

What enzyme is inactivated by aspirin?

A

Cyclo-oxygenase

70
Q

What hormone/final product is blocked w/ aspirin?

A

Thromboxane A2 (TXA2)

71
Q

How long does inactivation due to aspirin last?

A

For entire life of platelet → 8-12 days

Liz's Hemostasis/Coagulation (10 decks)

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