platelet evaluation

Question 1

describe a platelet

Answer 1

• small, biconcave
• in mammals is a nucleated
• is nucleated is called a thrombocyte
• all platelets are thrombocytes but not all thrombocytes are platelets

Question 2

which animals have nucleated platelets?

Answer 2

• birds
• reptiles

Question 3

thrombocytosis

Answer 3

• an increase in the number of circulating platelets

Question 4

thrombocytopenia

Answer 4

• decrease in the number of circulating platelets

Question 5

describe platelet production

Answer 5

• occurs in the bone marrow
• they come from a pluripotent stem cell that matures into myeloid progenitor then a megakaryocytic
• one stem cell can produce 2000-8000 platelets
• regulated by thrombopoietin (controlled by platelet mass)

Question 6

what cell to platelets come from

Answer 6

• stem cell
• megakaryocyte

Question 7

how many platelets can one stem cell produce

Answer 7

2000-8000

Question 8

which hormone regulates the production of platelets?

Answer 8

• thrombopoietin
  (controlled by circulating mass of platelets)

Question 9

how long do canine platelets circulate for?

Answer 9

5-10 days

Question 10

how long do cat platelets circulate for?

Answer 10

about 1 day

Question 11

what events do platelets help moderate? (5)

Answer 11

• inflammation
• thrombosis
• hemostasis
• fibrinogen
• coagulation

Question 12

what role do platelets play in inflammation?

Answer 12

• stimulate a local response to cell injury
• is marked by capillary dilation, leukocytic infiltration, redness, heat, and pain
• serves as a mechanism for initiating the elimination of agents and damaged tissue

Question 13

thrombosis

Answer 13

• the formation or the presence of a blood clot within a vessel
• thrombocytes coming together

Question 14

hemostasis

Answer 14

• stoppage of bleeding

Question 15

fibrinolysis

Answer 15

• the natural enzymatic breakdown of fibrin

Question 16

how do platelets aid in coagulation?

Answer 16

• causes the plasma to become viscous or thickened into a coherent mass

Question 17

what helps prevent excessive internal bleeding?

Answer 17

• adequate platelet numbers

Question 18

when does spontaneous bleeding start?

Answer 18

when platelet population is about <2/oil field

Question 19

macroplatelet

Answer 19

• large platelet
• as large or larger than a RBC
• more basophilic
• varying amounts of granulation
• is normal in feline and bovine blood
• is typically younger
• is a shift platelet

Question 20

what should we evaluate with platelets?

Answer 20

• number
• relative size
• shape (activated)
• granulation
• colour

Question 21

why are platelet numbers hard to evaluate?

Answer 21

• they are small
• irregularly distributed
• disintegrate in a sample
• tend to agglutinate

Question 22

what are platelets activated by?

Answer 22

surface contact

Question 23

ways to prevent platelet clumping in your blood sample

Answer 23

• mix the vacutainer well immediately
• avoid excessive tissue trauma during collection

Question 24

what methods can be used to evaluate platelet numbers?

Answer 24

• manual estimation
• LeukoCheck system
• automated cell counter

(are accurate unless the patient is anemic)

Question 25

when is an accurate platelet count not possible?

Answer 25

when there is platelet clumping

Question 26

what is the normal range of platelets under an HPF?

Answer 26

5-25

Question 27

what are the 3 main causes of thrombocytopenia?

Answer 27

- increased peripheral utilization - increased platelet destruction - reduced platelet production

Question 28

what are the causes of thrombocytosis?

Answer 28

- secondary or reactive to (most are secondary): 1. secondary to splenic contractions 2. splenectomy 3. fractures (because bone marrow is exposed)

Question 29

Whose platelets are larger, cats or dogs?

Answer 29

cats

Question 30

how large is the typical dog platelet?

Answer 30

- 1/3 to 1/2 the size of a normal RBC

Question 31

when is a platelet considered a macroplatelet (at what size)?

Answer 31

- when it is as large as a RBC

Question 32

in which species are macroplatelets common?

Answer 32

cats bovine

Question 33

What do platelets send out when stimulated, which gives them a 'hairy' appearance?

Answer 33

- pseudopods

Question 34

describe platelet granulation

Answer 34

- have a center granulomere (collection of granules) - peripheral hyalomere - the amount of granulation carries with species - the amount of granulation indicates the ability of the platelet to support the clotting reaction

Question 35

describe platelet colouration

Answer 35

- indicates age (dark= young)

Question 36

what does thrombocytopenia with increased basophilia indicate?

Answer 36

- indicates platelet production and utilization

Question 37

what does thrombocytopenia with decreased basophilia?

Answer 37

- normal platelet lifespan with decreased production

Question 38

what are 3 platelet habits?

Answer 38

- satellitism - pseudoinclusions - clumping

Question 39

describe platelet satelitism

Answer 39

- seen with EDTA - clumping of platelets around an RBC

Question 40

describe a platelet pseudoinclusion

Answer 40

- the platelet appears as an inclusion in the RBC - is of no significance

Question 41

what is a common platelet inclusion?

Answer 41

anaplasma platys

Question 42

describe anaplasma platys

Answer 42

- multiple small, blue-purple coccoid shapes called elementary bodies - causes severe thrombocytopenia and is therefore rarely seen on a smear