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RUSVM Clinical Pathology > Platelets and Platelet Disorders > Flashcards

Platelets and Platelet Disorders Flashcards

1
Q

Buccal Mucosal Bleeding Time (BMBT)

A

Make a standarize incision, blood blood gently and measure time for bleeding to cease

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2
Q

Hemostasis

A

Stoppage of blood

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3
Q

Thrombocytopenia due to destruction by modified live virus vaccination

A

May induce an immune response against the platelet → platelet aggregation → clearance

Occurs 3-10 days post vaccination

Avoid surgery

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4
Q

Sequestration of platelets in large vascular beds

A

Splenomegaly, splenic torsion, neoplasia

Hepatomegaly, portal hypertension

Vasodilation in endotoxic shock

Severe hypothermia

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5
Q

1/3 of platelet mass is in the

A

Spleen

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6
Q

What is the order of events in platelet plug formation?

A

Adhesion

Activation

Aggregation

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7
Q

Thrombocytopenia due to destruction can be caused by

A

Immune mediated thrombocytopenia (ITP)

Alloimmune thrombocytopenia

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8
Q

Laboratory tests used for platelet function

A

Bleeding time tests

Specific platelet function tests

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9
Q

Bone Marrow Aspirate (BMA)

A

Evaluate megakaryocyte number and morphology

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10
Q

Secondary or reactive thrombocytosis is associated with

A

Chronic Inflammatory Disease

Iron Deficiency Anemia

Chronic Hemorrhage

IMHA

Some neoplasms

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11
Q

Clinical signs associated with thrombocytopenia

A

Platelet bleeding pattern

Bleed from mucosal membranes

Petechiation to ecchymosis

+/- anemia

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12
Q

Cuticle (Toenail) Bleeding Time

A

Use a guillotine clipper and sever apex of nail, blot blood gently, and measure time for bleeding to stop

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13
Q

Pseudothrombocytopenia occurs because

A

Analyzer does not measure platelets because they are too big or clumped

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14
Q

Clot retraction and inflammation are involved in

A

Secondary Hemostasis

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15
Q

vWF is carrier for

A

Factor VIII

______________________________

Severe disease, may also have factor VIII deficiency

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16
Q

Vascular Injury causes:

A

Vasoconstriction

Activation of hemostasis

Platelets

Coagulation Factors

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17
Q

Major mechanisms of thrombocytosis

A

Increased production

Increased distribution in plasma

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18
Q

Two forms of von WIllebrand Disease (vWD)

A

Quantitative Deficiency (Type 1 and 3)

Qualitative abnormality (Type 2)

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19
Q

Granulation products secreted during the activation phase of primary hemostasis

A

Factors V and VIII

Thromboxane A2

Calcium

ADP

vWF

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20
Q

Thrombocytopenia due to decrease production can be the cause of

A

Bone marrow hypoplasia

Neoplasia

Myelonecrosis or myelofibrosis

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21
Q

Life span of platelets

A

5-10 days

___________________________________

Shorter in cats

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22
Q

Megakaryocytes

A

Large Cells

Polyploid nucleus

Abundant cytoplasm

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23
Q

Hemostasis requires the interaction of

A

Blood Vessels

Platelets

Coagulation Factors

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24
Q

Increased numbers of enlarged platelets suggests

A

Active production of platelets

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25
Q

Laboratory tests used for platelet concentration and morphology

A

Blood smear

Hematology analyzers

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26
Q

Bleeding Tests

A

Tests the ability of platelets to form a platelet plug - does not test fibrin plug formation

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27
Q

Clot Retraction occurs via

A

Actinomyosin filaments

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28
Q

Von Willebrand Factor (vWF)

A

Binds to GPIb on platelet surface

Bridge between platelet and collagen

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29
Q

Immunofluorescent Antimegakaryocytic Antibody Test

A

Detects antibodies on megakaryocytes

30
Q

Hemostasis is a balance between

A

Thrombus and hemorrhage

31
Q

Laboratory test used to evaluate anti-platelet antibodies

A

Platelet Surface-Associated Immunoglobulin (PSAIg)

Immunofluorescent Antimegakaryocytic Antibody Test

32
Q

Thrombus causes

A

Increased procoagulant activity or decreased fibrinolysis

33
Q

Hemorrhage causes

A

Decreased procoagulant activity

Decreased platelet number or loss of platelet function

Increased fibrinolysis

34
Q

Clot retraction facilitates

A

Wound closure

Vessel patency

35
Q

Bleeding tests are abnormal (prolonged) when:

A

Decreased platelet function

Decreased platelet numbers

36
Q

Pathology of thrombus

A

Excessive thrombus formation → obstructed blood flow → local hypoxia

37
Q

Maturation time of megakaryoblast to platelets

A

4-5 days

38
Q

Increased mean platelet volume (MPV) suggests

A

Increased thrombopoiesis

39
Q

Activation phase of primary hemostasis allows for

A

Recruitment of more platelets

Further platelet activation

Facilitate coagulation

Mediate vessel repair

40
Q

Clinical features of thrombocytopenia

A

Mucosal bleeding

Petechiation

Ecchymosis

Spontaneous hemorrhage

+/- hemorrhagic anemia

41
Q

Primary Hemostasis

A

Formation of a primary hemostatic plug

Take 3-5 minutes

  1. Platelets adhere to subendothelium
  2. Undergo activation
  3. Aggregate to form a platelet plug
42
Q

Aggregation phase of primary hemostasis

A

Irreversible

Mediated by ADP, Thromboxane A2

Thrombin = positive feedback

Ca required

43
Q

Acquired cause of qualitative platelet disorders

A

Uremia

Drugs

Fibrin Degradation Products (FDPs)

Paraproteins

44
Q

Increased concentration platelets associated with what situations

A

Rebound from thrombocytopenia

Response to some drugs

Post splenectomy

Excitment and exercise

Splenic contraction

45
Q

Secondary Hemostasis

A

Surface for formation and deposition of fibrin

Occurs on the platelet surface

46
Q

Describe the activation step of primary hemostasis

A
  1. Shape change - smooth discs to spheres with filopoida in response to thrombin
  2. Flip membrane - negative charge on outer membrane of platelet
  3. Secretion of granule products
47
Q

Fibrin Degradation Products (FDPs) cause aquired qualitative platelet disorders by

A

Inhibiting platelet function in disease processes

48
Q

Von Willebrand Disease (vWD)

A

No defects in platelets

Defect is in the adhesion molecule that binds platelets during initaition of platelet plug

Decreased platelet adhesion

49
Q

Mechanisms of thrombocytopenia

A

Decreased production

Destruction

Sequestration

Loss

Consumption

Pseudothrombocytopenia

50
Q

Thrombopoietin (TPO)

A

(+) Megakaryocyte production and differentiation

Continually produced by liver, bone marrow, endothelium, etc

Binds to receptors on platelets

51
Q

Inherited qualitative platelet disorders

A

Absence of glycoprotein receptors

Absence or reduction in platelet granules

Signal transduction defects

Von Willebrands Disease

52
Q

Suspect qualitative platelet disorder in an animal with

A

Clinical signs of thrombocytopenia

Normal platelet count

53
Q

Thrombocytopenia due to abnormal distribution of platelets

A

Seqestration of platelets in large vascular beds

54
Q

Thrombocytosis

A

Platelet count greater than upper reference interval

55
Q

Platelet Surface Associated Immunoglobuin (PSAIg)

A

Difficult to perform because platelets normally carry some immunoglobulin

56
Q

Laboratory tests for thrombocytopenia

A

Complete blood count (CBC) - severe thrombocytopenia

Other coag tests - PT, PTT will be normal

Bone marrow aspirate - increased megakaryocytes

Anti-platelet Antibody Tests - positive

Serum biochemistry - normal

57
Q

Alloimmune Thrombocytopenia

A

Dam produces antiplatelet antibody from a previous pregnancy

Offspring ingests antibody in the colostrum

58
Q

Alpha2Beta1 (GP Ia - IIa) and GP VI Receptors

A

Bind platelets directly to collagen

Initiate intracellular signaling → activation, adhesion

59
Q

Pathology of hemorrhage

A

Inability to form a thrombus → hemorrhage

60
Q

Thrombocytopenia

A

Platelet count less than lower reference interval

61
Q

Action of TPO on the bone marrow

A

Increase number, size and ploidy of megakaryocytes

Decreased megakaryocyte maturation time

62
Q

Laboratory test used for platelet production evaluation

A

Bone marrow aspirate (BMA)

63
Q

Clinical features of von Willebrand Disease

A

Mild to severe bleeding

Exacerbated by surgery or trauma

Signs decrease with age and successive pregnanacies

64
Q

Describe the morphology of platelets

A

Small granular discs

Membrane glycoproteins - receptors for ligands

Anucleate

Cytoskeleton

Alpha and dense granules

Canalicular and tubular systems

65
Q

Laboratory tests of von Willebrand Disease

A

Platelet count - normal

BMBT - prolonged

PTT/ACT - normal, but can be prolonged if Factor VIII deficient

66
Q

Beta1-tubulin gene mutation

A

CKCS

Point mutation

Alters cytoskeleton

Causes mactrothrombocytes - decreased platelets, increase platelet MCV

Usually asymptomatic

67
Q

Thrombocytopenia due to consumption can be caused by

A

Disseminated intravascular coagulation (DIC)

Vasculitis

Viral infection

68
Q

Macroplatelets are suggestive of

A

Increased platelet production

69
Q

Paraproteins cause aquired qualitative platelet disorders

A

Plasma cell myeloma → increased globulins coat platelet surface and inhibit function

70
Q

Regulation of thrombopoiesis by

A

Thrombopoietin (TPO)

RUSVM Clinical Pathology (22 decks)

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