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RUSVM Clinical Pathology > Platelets and Platelet Disorders > Flashcards

Platelets and Platelet Disorders Flashcards

(70 cards)

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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
Laboratory tests used for platelet concentration and morphology
Blood smear Hematology analyzers
26
Bleeding Tests
Tests the ability of platelets to form a platelet plug - does not test fibrin plug formation
27
Clot Retraction occurs via
Actinomyosin filaments
28
Von Willebrand Factor (vWF)
Binds to GPIb on platelet surface Bridge between platelet and collagen
29
Immunofluorescent Antimegakaryocytic Antibody Test
Detects antibodies on megakaryocytes
30
Hemostasis is a balance between
Thrombus and hemorrhage
31
Laboratory test used to evaluate anti-platelet antibodies
Platelet Surface-Associated Immunoglobulin (PSAIg) Immunofluorescent Antimegakaryocytic Antibody Test
32
Thrombus causes
Increased procoagulant activity or decreased fibrinolysis
33
Hemorrhage causes
Decreased procoagulant activity Decreased platelet number or loss of platelet function Increased fibrinolysis
34
Clot retraction facilitates
Wound closure Vessel patency
35
Bleeding tests are abnormal (prolonged) when:
Decreased platelet function Decreased platelet numbers
36
Pathology of thrombus
Excessive thrombus formation → obstructed blood flow → local hypoxia
37
Maturation time of megakaryoblast to platelets
4-5 days
38
Increased mean platelet volume (MPV) suggests
Increased thrombopoiesis
39
Activation phase of primary hemostasis allows for
Recruitment of more platelets Further platelet activation Facilitate coagulation Mediate vessel repair
40
Clinical features of thrombocytopenia
Mucosal bleeding Petechiation Ecchymosis Spontaneous hemorrhage +/- hemorrhagic anemia
41
Primary Hemostasis
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
Aggregation phase of primary hemostasis
Irreversible Mediated by ADP, Thromboxane A2 Thrombin = positive feedback Ca required
43
Acquired cause of qualitative platelet disorders
Uremia Drugs Fibrin Degradation Products (FDPs) Paraproteins
44
Increased concentration platelets associated with what situations
Rebound from thrombocytopenia Response to some drugs Post splenectomy Excitment and exercise Splenic contraction
45
Secondary Hemostasis
Surface for formation and deposition of fibrin Occurs on the platelet surface
46
Describe the activation step of primary hemostasis
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
Fibrin Degradation Products (FDPs) cause aquired qualitative platelet disorders by
Inhibiting platelet function in disease processes
48
Von Willebrand Disease (vWD)
No defects in platelets Defect is in the adhesion molecule that binds platelets during initaition of platelet plug Decreased platelet adhesion
49
Mechanisms of thrombocytopenia
Decreased production Destruction Sequestration Loss Consumption Pseudothrombocytopenia
50
Thrombopoietin (TPO)
(+) Megakaryocyte production and differentiation Continually produced by liver, bone marrow, endothelium, etc Binds to receptors on platelets
51
Inherited qualitative platelet disorders
Absence of glycoprotein receptors Absence or reduction in platelet granules Signal transduction defects Von Willebrands Disease
52
Suspect qualitative platelet disorder in an animal with
Clinical signs of thrombocytopenia Normal platelet count
53
Thrombocytopenia due to abnormal distribution of platelets
Seqestration of platelets in large vascular beds
54
Thrombocytosis
Platelet count greater than upper reference interval
55
Platelet Surface Associated Immunoglobuin (PSAIg)
Difficult to perform because platelets normally carry some immunoglobulin
56
Laboratory tests for thrombocytopenia
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
Alloimmune Thrombocytopenia
Dam produces antiplatelet antibody from a previous pregnancy Offspring ingests antibody in the colostrum
58
Alpha2Beta1 (GP Ia - IIa) and GP VI Receptors
Bind platelets directly to collagen Initiate intracellular signaling → activation, adhesion
59
Pathology of hemorrhage
Inability to form a thrombus → hemorrhage
60
Thrombocytopenia
Platelet count less than lower reference interval
61
Action of TPO on the bone marrow
Increase number, size and ploidy of megakaryocytes Decreased megakaryocyte maturation time
62
Laboratory test used for platelet production evaluation
Bone marrow aspirate (BMA)
63
Clinical features of von Willebrand Disease
Mild to severe bleeding Exacerbated by surgery or trauma Signs decrease with age and successive pregnanacies
64
Describe the morphology of platelets
Small granular discs Membrane glycoproteins - receptors for ligands Anucleate Cytoskeleton Alpha and dense granules Canalicular and tubular systems
65
Laboratory tests of von Willebrand Disease
Platelet count - normal BMBT - prolonged PTT/ACT - normal, but can be prolonged if Factor VIII deficient
66
Beta1-tubulin gene mutation
CKCS Point mutation Alters cytoskeleton Causes mactrothrombocytes - decreased platelets, increase platelet MCV Usually asymptomatic
67
Thrombocytopenia due to consumption can be caused by
Disseminated intravascular coagulation (DIC) Vasculitis Viral infection
68
Macroplatelets are suggestive of
Increased platelet production
69
Paraproteins cause aquired qualitative platelet disorders
Plasma cell myeloma → increased globulins coat platelet surface and inhibit function
70
Regulation of thrombopoiesis by
Thrombopoietin (TPO)

RUSVM Clinical Pathology (22 decks)

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