Platelets

Question 1

What is the process of thrombus formation during vascular injury?

Answer 1

Vasoconstriction and activation of hemostasis

Primary hemostatic plug of platelets

Secondary hemostatic plug of fibrin

Question 2

When you have an imbalance in hemostatis what are the two main outcomes?

Answer 2

Thrombus

Hemorrhage

Question 3

Thrombus can be formed due to increased __________ activity or decreased ____________

Answer 3

Procoagulant; fibrinolysis

Question 4

Hemorrhage can be caused by a decreased in __________________ or __________________, and an increase in _______________

Answer 4

Procoagulant activity, platelet number/function; fibrinolyisis

Question 5

What is the lifespan of a platelet?

Answer 5

5-10days

Question 6

How much of the platelet mass in in the spleen?

Answer 6

1/3

Question 7

What is the sequence of maturation of a platelet?

Answer 7

Stem cell -> megakayroblast -> megakaryocytes -> platelet

Question 8

How are platelets formed form megakaryocytes ?

Answer 8

Megakaryocytes are located in the bone marrow

Long pro platelet processes extend into sinus lumen

Individual platelets break off

Question 9

What hormone regulates the production of platelets? Where is it produced?

Answer 9

Thrombopoeitin (TPO)

Liver, kidney, muscle

Question 10

If the number of platelets decreases, the amount of free TPO _____________

Answer 10

Increases

Question 11

What are the two main effects of TPO in the bone marrow

Answer 11

Increase number, size and policy of megakaryocytes

Decreased maturation time of megakaryocytes

Question 12

How long does it take to form a primary hemostatic plug?

Answer 12

3 to 5 mins

Question 13

What are the stages of formation of the primary hemostatic plug?

Answer 13

Adhere
Activate
Secretion
Aggregation

Question 14

What factor is involved in the adhesion phase of primary hemostatis

Answer 14

Von willebrand factor

-binds to GPlb on PLT surface

Question 15

What occurs in the activation of platelets?

Answer 15

Shape change in response to thrombin
-shift from smooth disc to sphere with filopodia

Flips membrane phosphatidylserine
-negative charge on the outer membrane surface

Secretion of granule products -> factor V and VIII, thromboxane A2, an Ca

Question 16

Is the aggregations of platelets reversible, or irreversible?

Answer 16

Irreversible

Question 17

Secondary hemostasis involves the deposition of __________

Answer 17

Fibrin

Question 18

How are platelet clots are retracted via ?

Answer 18

Actinomyosin filaments

-> wound closure and vessel patency

Question 19

What tests measure the platelet concentration and morphology?

Answer 19

Blood smear

Hematology analyzers

Question 20

What tests can measure function of planets?

Answer 20

Bleeding time tests

Specific platelet function test

Question 21

What test can you do to determine platelet production?

Answer 21

Bone marrow aspirate (BMA)

Question 22

Why should you collect your blood samples in a purple top tube for determining platelet function?

Answer 22

contains EDTA -> Ca chelator -> prevent clotting

Question 23

What is the minimum concentration of platelets in a blood smear?

Answer 23

7-10 PLT/high power field

Except in horse 4-7

Question 24

Patients are at risk for spontaneous hemorrhage when the platelet count is < ___________

Answer 24

30,000/ uL

Question 25

An increased mean platelet volume suggests ____________

Answer 25

Thrombopoiesis

Question 26

Bleeding time tests can be abnormal when ?

Answer 26

Decreased platelet function Decreased platelet numbers

Question 27

What are clinical features of thrombocytopenia?

Answer 27

``` Mucosal bleeding Petechiation Ecchymosis Spontaneous hemorrhage : <30,000/ul Hemorrhagic aneimia ```

Question 28

What are the mechanisms of thrombocytopenia?

Answer 28

``` Decreased production Destruction Sequestration Loss Consumption ``` Pseduothrombocytopenia

Question 29

What can causes decreased production of platelets?

Answer 29

Bone marrow hypoplasia Neoplasia (primary or metastatic leukemia) Myelonecrosis or myelofibrosis (Affecting only megakaryocytes or multiple cell lines)

Question 30

What can cause destruction of platelets?

Answer 30

Immune mediated thrombocytopenia Alloimmune thrombocytopenia Modified live virus vaccination

Question 31

Piglets have high mortality rates from hemorrhage due to what disease?

Answer 31

Alloimmune thrombocytopenia Dam produces anti-platelet antibodies from a previous pregnancy

Question 32

How does a modified live virus vaccination cause platelet destruction ?

Answer 32

Vaccination can induce immune response against the PLT -> platelet aggregation -> clearance Occur 3-10days post vaccination

Question 33

How are platelets sequestered ?

Answer 33

In large vascular beds - splenomegaly, scenic torsion, neoplasia - hepatomegaly, portal hypertension - vasodilation in endotoxic shock

Question 34

T/F: Hemorrhage can cause thrombocytopenia

Answer 34

FALSE Acute severe hemorrhage may result in mild thrombocytopenia

Question 35

What are common causes of consumption causing thrombocytopenia?

Answer 35

Disseminated intravascular coagulation (DIC) | Vasculitis (rickettsial or FIP)

Question 36

What is pseudothrombocytopenia?

Answer 36

False thrombocytopenia because the analyazer doesn't measure the platelets because they are 1. Too big 2. Clumped

Question 37

What are the two major mechanisms of thrombocytoisis?

Answer 37

Increased production Increased distribution in plasma

Question 38

A thrombocytoisis can be associated with what diseases?

Answer 38

``` Chronic inflammatory disease (eg IMHA) Chronic hemorrhage (IDA) ```

Question 39

If you have a normal platelet count but the patient has clinical signs of thrombocytopenia, what might you suspect?

Answer 39

Qualitative disorder of platelets

Question 40

What are acquired causes of qualitative disorders of platelets?

Answer 40

Uremia Drugs Fibrin desecration products - inhibit PLT function in disease process Paraprotiens -plasma cell myeloma cause increased globulins coating PLT surface

Question 41

What are inherited qualitative disorders of platelets?

Answer 41

Absences of glycoproteins receptors Absence/reduction in platelet granules Single transduction defects Von willebrands disease

Question 42

T/F: in von Willebrands disease, platelets are usually normal

Answer 42

True Defect is in the von Willebrands factor that in in endothelial wall

Question 43

What are the two types of von willebrands disease?

Answer 43

Quantitative deficiency (type 1 and 3) Qualitative abnormality (type 2)

Question 44

What breed of dog is predisposed to vonWillebrands disease ?

Answer 44

Doberman