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Hemic-Lymphatic and Clin Path > Platelets > Flashcards

Platelets Flashcards

1
Q

how long do platelets circulate in the blood?

A

5-10 days

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2
Q

what do platelets provide?

A

primary hemostasis: sealing of small vascular defects/leaks

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3
Q

what are feline platelets like?

A

normally vary widely in size

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4
Q

what dogs breeds have lower platelet counts?

A

greyhound
shiba inu
cavalier king charles spaniel

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5
Q

when does spontaneous hemorrhage due to thrombocytopenia occur?

A

platelet count markedly decreased: dogs <30,000/microliter

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6
Q

what is pseudothrombocytopenia?

A

false decrease in platelet count

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7
Q

what is pseudothrombocytopenia most commonly caused by?

A

platelet clumping

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8
Q

what can cause decreased production of platelets?

A

damage to stem cells or microenvironment
suppression of thrombopoiesis or hematopoiesis

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9
Q

what are some causes of thrombocytopenia?

A

pseudothrombocytopenia
decreased production
increased consumption
increased destruction
blood loss (less common)
sequestration

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10
Q

what are some general causes of decreased platelet production?

A

drug-induced/toxic (uncommon)
infectious diseases
bone marrow neoplasia or fibrosis
aplastic anemia

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11
Q

what destroys platelets?

A

macrophage phagocytosis

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12
Q

what are some causes of accelerated platelet consumption?

A

vascular lesions
increased activation of coagulation

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13
Q

how can immune thrombocytopenia be diagnosed?

A

very low platelet counts typically
exclusion of other diseases and/or response to therapy
anti-platelet antibody testing?

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14
Q

does hemorrhage always cause thrombocytopenia?

A

not always
severe hemorrhage can cause marked thrombocytopenia

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15
Q

what are the general causes of thrombocytosis?

A

physiologic
reactive
neoplastic

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16
Q

what is physiologic thrombocytosis like?

A

mild and transient

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17
Q

what is physiologic thrombocytosis from?

A

increased mobilization from splenic and non-splenic pools
stress, exercise, pregnancy

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18
Q

how can inflammation cause reactive thrombocytosis?

A

promotes production of thrombopoietin

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19
Q

when are platelet function defects suspected?

A

when there is evidence of abnormal primary hemostasis with normal platelet numbers

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20
Q

what are some platelet function tests?

A

buccal mucosal bleeding time
thromboelastography
platelet function analyzer

21
Q

what is the most common hereditary platelet disorder in dogs?

A

von willebrand’s disease

22
Q

what is von willebrand’s disease?

A

disorder of platelet function caused by a deficiency in functional von willebrand’s factor (abnormal amounts +/- multimer distribution)

23
Q

what are the two categories of acquired platelet dysfunction?

A

drug-induced
non-drug-induced

24
Q

how do platelets leave circulation?

A

utilization/consumption
phagocytized by liver

25
Q

what color granules are often seen in mammalian platelets?

A

reddish-purple

26
Q

what do alpha granules contain?

A

platelet factor 4
fibrinogen
coagulation factors V, VII, XI, XIII
P selectin
plasminogen activator inhibitor
tissue factor pathway inhibitor

27
Q

what do dense granules contain?

A

nucelotides
calcium and magnesium
serotonin and histamine

28
Q

when can dense granules be seen?

A

electron microscopy

29
Q

what tends to happen with platelets with increased regeneration?

A

larger and more variation in size

30
Q

what species’ platelets have a strong tendency to clump in blood tubes?

A

feline
rabbit
cattle

31
Q

what do bird and reptile thrombocytes look like?

A

basophilic nuclei with clear or light blue cytoplasm

32
Q

how do primary hemostatic defects manifest?

A

petechiae
ecchymoses
mucosal bleeding
excessive post-op bleeding

33
Q

what do cavalier king charles spaniels often have a mutation in?

A

platelet microtubules

34
Q

what influences platelet count?

A

production
consumption
destruction
sequestration or release from spleen and lung

35
Q

what can decreased production of platelets cause?

A

moderately to markedly decreased platelet counts

36
Q

what does consumption of platelets result in?

A

mildly to moderately decreased platelet numbers

37
Q

what are some vascular lesions that can cause accelerated platelet consumption?

A

internal trauma
vasculitis
vascular neoplasia

38
Q

what can cause increased activation of coagulation?

A

disseminated intravascular coagulation
snake envenomation

39
Q

what can cause secondary immune thrombocytopenia?

A

drugs
infectious agents
paraneoplastic syndrome

40
Q

what can cause thrombocytopenia in cats?

A

rule out clumping
infectious/viral diseases
neoplasia
cardiac disease
multiple diseases
primary ITP uncommon

41
Q

what can cause reactive thrombocytosis?

A

inflammation
neoplasia
iron deficiency/hemorrhage
rebound thrombopoiesis after thrombocytopenia
drug-related
post-splenectomy

42
Q

what are some neoplasias of platelets/thrombocytes?

A

essential thrombocythemia: very rare
megakaryocyte leukemia: rare

43
Q

what agonists being exposed lead to platelet activation?

A

collagen
ADP
thromboxane A2
serotonin

44
Q

what does intact endothelium secrete to inhibit platelet activation?

A

prostacyclin

45
Q

what is thromboxane A2 produced by?

A

platelets with arachidonic acid metabolism

46
Q

what does thromboxane A2 promote?

A

vasoconstriction
platelet activation
platelet aggregation

47
Q

what does GPIIb/IIIa bind to?

A

fibrinogen
von willebrand’s factor
fibronectin

48
Q

what are the functions of von willebrand’s factor?

A

platelet adhesion
clotting factor VIII binding

49
Q

in whom is von willebrand’s disease uncommon?

A

horses
cattle
pigs
very rare in cats

Hemic-Lymphatic and Clin Path (33 decks)

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