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Heme and Lymph Exam 2 > Platelets - R. Gianani - SRS > Flashcards

Platelets - R. Gianani - SRS Flashcards

1
Q

What is this?

A

Megakaryocyte

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2
Q

What is this?

A

Platelet

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3
Q

Describe the physical appearance of a platelet

A

Small, disc shaped anucleate cells with tiny visible rim of cytoplasm surrounding a granular center.

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4
Q

What types of granules do platelets contain?

A

Alpha granules

Delta granules

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5
Q

What do alpha granules contain?

2 functional categories with three components each

A

Coagulation factors

  1. fibrinogen
  2. Factor V
  3. vWF

Wound healing factors

  1. fibronectin
  2. platelet factor 4
  3. PDGF
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6
Q

What does the membrane of alpha granules contain?

A

P-selectin

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7
Q

What do delta granules contain?

A

ADP

ATP

Ionized calcium

Serotonine

Epinephrine

(ESAAC)

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8
Q

Following blood vessel injury a number of physiological events take place aiming at restoring vessel integrity. Both platelets and soluble molecules. take part in these events. What does the repair of the vessel culminate in?

A

Formation of secondary hemostatic plug and wound helaing (re-endothelization)

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9
Q

What are the phases of platelet activation?

A
  1. adhesion
  2. activation
  3. aggregation
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10
Q

What receptors are involved in the adhesion step of the platelet reaction?

A

GpIb and vWF on exposed collagen

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11
Q

What are the two components of the activation step of the platelet reaction?

A
  1. Change of shape
  2. Secretion
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12
Q

What does the change of shape during platelet activation lead to?

A
  1. Increased surface area and Increased affinity of GpIIb/IIIa and fibrinogen.
  2. Translocation of calcium binding negatively charged phospholipids to the surface of the cells.
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13
Q

What is involved in the aggregation phase of the platelet reaction?

A

Binding of GpIIB to fibrinogen. Initial reversible phase followed by thrombin induced further platelet activation aggregation and irreversible platelet contraction.

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14
Q

What are four broad mechanisms of thrombocytopenia?

A
  1. decreased production
  2. decreased survival
  3. sequestration
  4. dilution
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15
Q

What are some examples of disease states that decrease platelet production?

A
  1. Selective impairment of platelet production
  2. Drug-induced: alcohol, thiazides, cytotoxic drugs
  3. Infections: measles, human immunodeficiency virus (HIV)
  4. Nutritional deficiencies
  5. B12, folate deficiency (megaloblastic leukemia)
  6. Bone marrow failure
  7. Aplastic anemia
  8. Bone marrow replacement
  9. Leukemia, disseminated cancer, granulomatous disease
  10. Ineffective thrombopoiesis .
  11. Myelodysplastic syndromes
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16
Q

What are three broad categories of conditions that decrease platelet survival?

A

Primary autoimmune

Secondary autoimmune

Nonimmunologic destruction

17
Q

What are two examples of primary autoimmune platelet destruction?

A
  1. Chronic immune thrombocytopenia
  2. acute immune thrombocytopenic purpura
18
Q

What are four examples of secondary autoimmune platelet destruction?

A
  1. Systemic lupus erythematosus, B-cell lymphoid neoplasms
  2. Alloimmune: posttransfusion and neonatal
  3. Drug-associated: quinidine, heparin, sulfa compounds
  4. Infections
19
Q

What are some infections that cause secondary autoimmune platelet destruction? 3

A
  1. HIV
  2. infectious mononucleosis (transient, mild)
  3. dengue fever
20
Q

What are three nonimmunologic examples of platelet destruction?

A
  1. Disseminated intravascular coagulation
  2. Thrombotic microangiopathies
  3. Giant hemangiomas
21
Q

What is the cause of platelet sequestration?

A

hypersplenism

22
Q

What is the cause of dilution of platelets?

A

Transfusion

23
Q

When enumerating platelets, you can see falsely low platelet counts - pseudothrombocytopenia.

What are some examples of causes of pseudothrombocytopenia?

A
  1. Platelet agglutinins
  2. paraproteinemias
  3. giant platelets
  4. lipemia
  5. EDTA induced platelet clumping
24
Q

You can also see falsely high platelet counts. What are three causes of this?

A

Microspherocytes

WBC/RBC fragments

Pappenheimer bodies

25
Q

What are the two main causes of thrombotic thrombocytopenic purpura/hemolytic uremic syndrome?

A
  • Deficiency of ADAMTS13 - either acquired or inherited
  • Infection - primarily E. coli 0157:H7
26
Q

What causes typical HUS?

A

E. Coli 0157:H7 via Shiga-like toxin

27
Q

What is the distinction between TTP and HUS?

A

Disorders in adults are typically described as TTP and are relatively less likely to involve renal failure. Also, neurological complications are more likely in TTP.

Disorders in children are typically described as HUS, and are relatively more likely to involve renal failure. Neurological problems less common in HUS.

**Per MERK manual**

Also,

28
Q

What are atypical causes of TTP/HUS?

A

Alternative pathway inhibitor deficiencies

(complement factor H, mebrane cofactor protein (CD46), or factor I.

29
Q

What are some miscellaneous associations with TTP/HUS?

A
  1. Drugs (cyclosporine, chemotherapeutic agents)
  2. Radiation, bone marrow transplantation
  3. Other infections (HIV, pneumococcal sepsis)
  4. Conditions associated with autoimmunity (systemic lupus erythematosus, HIV infection, lymphoid neoplasms)
30
Q
A

Heme and Lymph Exam 2 (9 decks)

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