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Clinical Pathology > Homeostasis and Platelet Disorders > Flashcards

Homeostasis and Platelet Disorders Flashcards

0
Q

What does “hemo” mean?

A

Blood

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1
Q

The stoppage of blood is known as what?

A

Hemostasis

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2
Q

What does “stasis” mean?

A

Stop

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3
Q

To achieve hemostasis without obstructing blood flow is what?

A

The goal.

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4
Q

Formation of a thrombus leads to what?

A

A blood clot

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5
Q

Hemostasis involves the interaction of what 3 components?

A
  • Blood vessels
  • Platelets
  • Coagulation factors
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6
Q

After injury to a blood vessel, what 3 steps are seen?

A
  • Vessel constriction
  • Platelet adhesion (primary hemostasis)
  • Activation of coagulation (secondary hemostasis)
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7
Q

What can thrombosis inhibit?

A

Blood loss/consumption

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8
Q

What can cause thrombosis?

A

Increased procoagulant activity

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9
Q

What are 3 causes hemorrhage?

A
  • Decreased procoagulant activity
  • Thrombocytosis (decreased platelet function)
  • Excessive fibrinolysis
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10
Q

The secondary hemostatic plug is also known as what?

A

Definitive fibrin plug

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11
Q

What is the average size of a platelet?

A

2-4 um

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12
Q

Do platelets have a nucleus?

A

No

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13
Q

What are 3 things that can be found in a platelet?

A
  • Cytoskeleton
  • Alpha and dense granules
  • Canalicular and tubular systems
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14
Q

What act as receptors for ligands on platelets?

A

Membrane glycoproteins

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15
Q

What are suggestive of increased platelet production?

A

Large and giant platelets

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16
Q

What is the process of thrombopoiesis?

A
  • Stem cell
  • Megakaryoblast
  • Megakaryocyte
  • Platelets
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17
Q

What type of a nucleus do megakaryocytes have?

A

Polyploid nucleus (8N-64N)

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18
Q

Are megakaryocytes small or large cells?

A

Large cells

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19
Q

Do megakaryotes have abundant cytoplasm?

A

Yes

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20
Q

Where are megakaryocytes located?

A

At the sinus

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21
Q

What do megakaryocytes break into?

A

Individual platelets

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22
Q

What is the maturation time of Megakaryoblast to platelet release?

A

4-5 days

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23
Q

What is thrombopoiesis regulated by?

A

Thrombopoietin (TPO)

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24
Q

What does Thrombopoietin stimulate?

A

Increased megakaryocyte production and differentiation.

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25
Q

Where are 3 places where thrombopoietin is continually produced?

A
  • Liver
  • Basement membrane
  • Endothelium
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26
Q

A decrease in platelet numbers leads to what?

A

Increased free plasma TPO

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27
Q

What are 2 effects of an increase in free plasma TPO?

A
  • Increase number , size and ploidy of megakaryocytes

- Decrease in megakaryocyte maturation time.

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28
Q

What is the average life span of a platelet?

In what species is this time shorter?

A
  • About 5-10 days

- Shorter in cats.

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29
Q

Where can you find about 1/3 of the platelet mass?

A

In the spleen.

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30
Q

What are 3 functions of platelets?

A
  • Increase metabolic activity
  • Primary Hemostasis
  • Support secondary hemostasis
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31
Q

Formation of a primary hemostatic plug takes about how long?

A

3-5 minutes

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32
Q

What do platelets adhere to during primary hemostatic plug formation?

A

Subendothelium

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33
Q

What are the 4 steps of primary hemostatic plug formation?

A
  • Adhere
  • Activation
  • Secrete
  • Aggregate
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34
Q

What happens to the platelets during the activation stage of the primary hemostatic plug formation?

A

They change shape.

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35
Q

What do platelets secrete during primary hemostatic plug formation?

A

Their granules.

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36
Q

When platelets aggregate, what do they form?

A

A platelet plug.

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37
Q

What are 4 components required during the adhesion stage of primary hemostasis?

A
  • von Willebrand Factor (vWF)
  • ADP
  • CA2+
  • Serotonin
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38
Q

What are 2 functions of von Willebrand Factor (vWF)?

A
  • Binds to GPlb on platelet surface.

- Bridge between platelets and collagen.

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39
Q

How do the shapes of platelets change during the activation stage of primary hemostasis?

A

From smooth discs to spheres with many filapodia.

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40
Q

Change in platelet shape occurs in response to what?

A

Thrombin

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41
Q

How does the platelet shape change affect surface area seen in primary hemostasis?

A

Increases the surface area.

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42
Q

What are 3 things that are secreted by platelets during the activation stage of primary hemostasis?

A
  • Factors V and VIII
  • Thromboxane A2
  • Calcium (Ca2+)
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43
Q

The secretion of granule products by platelets seen during the activation stage of primary hemostasis can what 4 effects?

A
  • Recruit more platelets
  • Further platelet activation
  • Facilitate coagulation
  • Mediate vessel repair
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44
Q

Platelets carry a negative charge on their outer membrane surface during what stage of primary hemostasis?

A

Activation

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45
Q

Is platelet aggregation during primary hemostasis a reversible or irreversible process?

A

Irreversible process

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46
Q

What binds activated platelets and bridges adjacent platelets during aggregation of primary hemostasis?

A

Fibrinogen

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47
Q

What is required for the aggregation stage of primary hemostasis?

A

Ca2+

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48
Q

What is the end result of primary hemostasis?

A

Platelet plug formation

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49
Q

Platelets provide a surface for what during primary hemostasis?

A

Formation and deposition of fibrin.

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50
Q

How do clots contract?

A

Via actinomyosin filaments

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51
Q

What are 2 things clot retraction facilitates?

A
  • Wound closure

- Vessel patency

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52
Q

Platelet chemotaxis enhances what?

A

Neutrophil function.

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53
Q

Do platelets have antimicrobial activity?

A

Yes

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54
Q

Platelets are sources of what 3 factors of inflammation?

A
  • Inflammatory mediators
  • Vasoactive substances
  • Mitogenic agents
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55
Q

What are 2 ways to test platelet concentration and morphology (size)?

A
  • Blood smear

- Hematology analyzers

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56
Q

What are 2 ways to test platelet function?

A
  • Bleeding time tests

- Specific platelet function tests

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57
Q

What is a way to test platelet production?

A

Bone marrow aspirate (BMA)

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58
Q

What are 2 ways to test for anti-platelet antibodies?

A
  • Platelet surface-associated immunoglobulin (PSAIg)

- Immunofluorescent antimegakaryocytic antibody test

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59
Q

To test for platelet concentration in blood, the blood should be collected in what type of tube?

A

Purple top - EDTA tube

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60
Q

What technique is the most important with drawing blood for the platelet concentration tests?

A

Venipuncture

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61
Q

When analyzing a blood smear for platelet concentration, about how many platelets are normally seen per high power field (100x)?
What is the minimum for horses?

A
  • 7-10 platelets per field

- Minimum of 4-7 platelets per field

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62
Q

When examining a blood smear for platelet counts, you should check for clumps, especially with what 2 species?

A
  • Cats

- Cattle

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63
Q

In general, are platelets smaller or larger than RBCs?

A

Smaller

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64
Q

More size variation of platelets is seen in what species?

A

Cats

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65
Q

Pale-staining platelets can be seen in what species?

A

Horses

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66
Q

What does increased numbers of enlarged platelets suggest?

A

Active production of platelets.

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67
Q

When the platelet count is lower than the lower end of the reference interval (LRI), what condition exists?

A

Thrombocytopenia

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68
Q

When the platelet count is greater than the upper reference interval (URI), what condition is present?

A

Thrombocytosis

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69
Q

You may see spontaneous hemorrhage when platelet counts are below what level?

A

20,000/uL

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70
Q

What does MPV stand for?

A

Mean platelet volume

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71
Q

What does increased MPV suggest?

A

Increased thrombopoiesis

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72
Q

Platelet function bleeding tests test the ability of platelets to do what?

A

Form a platelet plug.

73
Q

Do platelet function bleeding tests test fibrin plug formation?

A

No

74
Q

What does BMBT stand for?

A

Buccal mucosal bleeding time

75
Q

What are the 3 steps of testing platelet function using BMBT?

A
  • Make a standardized incision
  • Blot blood gently
  • Measure time for bleeding to cease
76
Q

What is normal buccal mucosal bleeding time (BMBT) for dogs?
For cats?
For horses/cattle?

A
  • Dogs: 1-5 minutes
  • Cats: 1-3.5 minutes
  • Horses/cattle: 8-10 minutes
77
Q

What are the 3 steps of the cuticle (toenail) bleeding time test?

A
  • Use a guillotine clipper and sever apex of nail
  • Blot blood gently
  • Measure time for bleeding to cease
78
Q

What is the normal cuticle (toenail) bleeding time for dogs?

A

2-8 minutes

79
Q

What are 3 examples of specific platelet function tests that require special equipment?

A
  • Adhesion
  • Aggregation
  • Secretion
80
Q

What does BMA stand for?

What is it used to evaluate?

A
  • Bone marrow aspirate

- Megakaryocyte number and morphology

81
Q

Why are platelet surface-associated immunoglobulin tests difficult to perform?

A

Platelets normally carry some immunoglobulin.

82
Q

What does the immunofluorescent antimegakaryocytic antibody test detect?

A

Antibodies on Megakaryocytes

83
Q

Is thrombocytopenia a specific disease?

A

No

84
Q

What are 5 clinical features seen with thrombocytopenia?

A
  • Mucosal bleeding
  • Petechiation
  • Ecchymosis
  • Spontaneous hemorrhage with platelets counts below 20,000/uL
  • May or may not have hemorrhagic anemia
85
Q

What are 6 possible mechanisms behind of thrombocytopenia?

A
  • Loss
  • Consumption
  • Destruction
  • Decreased production
  • Abnormal distribution
  • Pseudothromboctopenia
86
Q

Does hemorrhage alone usually cause significant thrombocytopenia?
What is an exception?

A
  • No

- Acute severe hemorrhage may result in mild thrombocytopenia

87
Q

What is a possible cause of consumption of platelets?

A

Utilization of platelets during coagulation.

88
Q

What are 3 possible causes of thrombocytopenia by consumption?

A
  • Disseminated intravascular coagulation (DIC)
  • Vasculitis (rickettsial disease, FIP)
  • Viral infection
89
Q

What range of degree of thrombocytopenia can be seen with consumption?

A

Mild to moderate

90
Q

Coagulation defects (DIC) or leakage of blood from vessels (vasculitis) can lead to what?

A

Hemorrhage

91
Q

What are 2 examples of destruction thrombocytopenia?

A
  • Immune-mediated thrombocytopenia (ITP)

- Alloimmune thrombocytopenia

92
Q

Primary Immune-mediated thrombocytopenia is often what?

A

Idiopathic

93
Q

What are 4 examples of causes of secondary immune-mediated thrombocytopenia?

A
  • Drugs
  • Viruses
  • Sepsis
  • Neoplasia
94
Q

Alloimmune thrombocytopenia can be seen in what 2 species?

A
  • Piglets

- Foals

95
Q

What does the dam produce with alloimmune thrombocytopenia?

A

Anti-platelet antibody from a previous pregnancy.

96
Q

What do the offspring ingest with alloimmune thrombocytopenia?

A

Antibody in the colostrum.

97
Q

Piglets with alloimmune thrombocytopenia have a high mortality rate from what?

A

Hemorrhage

98
Q

What type of vaccination may induce an immune response against the platelets, leading to platelet aggregation and clearance?

A

Modified-live virus vaccination

99
Q

Thrombocytopenia due to vaccination usually occurs when?

A

3-10 days post-vaccination

100
Q

Is thrombocytopenia seen with vaccines usually mild or severe?

A

Mild

101
Q

A complete blood count (CBC) can detect what type of thrombocytopenia?

A

Severe thrombocytopenia

102
Q

Bone marrow aspirates are used to detect what?

A

Increased megakaryocytes (immature & mature)

103
Q

What are 3 possible causes of decreased production of platelets?

A
  • Bone marrow hypoplasia
  • Neoplasia
  • Myelonecrosis or myelofibrosis
104
Q

The degree of thrombocytopenia seen with decreased production depends on what?

A

Extent of bone marrow disease.

105
Q

What is the most common form of abnormal distribution of platelets?

A

Sequestration of platelets in large vascular beds.

106
Q

What level of thrombocytopenia is seen with abnormal distribution of platelets?

A

Mild to moderate thrombocytopenia

107
Q

What are 2 possible reason an analyzer might not measure platelets, leading to pseudothrombocytopenia?

A
  • Too big (macrothrombocytes)

- Clumped

108
Q

An increased concentration of platelets is known as what?

A

Thrombocytosis

109
Q

What are 2 major mechanisms of thrombocytosis?

A
  • Increased production

- Increased distribution in plasma

110
Q

What type of symptoms are usually seen in animals with an increased platelet count?

A

Animals are usually asymptomatic.

111
Q

What are 2 possible reasons for increased concentration of platelets?
Which one is more common?

A
  • Primary neoplastic production of platelets

- Secondary or reactive thrombocytosis (more common)

112
Q

What are 5 possible causes of secondary or reactive thrombocytosis?
Which is the most common?

A
  • Chronic inflammatory disease (most common)
  • Iron deficiency anemia
  • Chronic hemorrhage
  • IMHA
  • Some neoplasms
113
Q

Increased concentration of platelets can be associated with what 4 situations?

A
  • Rebound from thrombocytopenia
  • Post-splenectomy
  • Response to some drugs (vincristine)
  • Excitement and exercise (epinephrine)
114
Q

Platelet qualitative disorders may be suspected in animals with what 2 conditions?

A
  • Clinical signs of thrombocytopenia (mucosal bleeding, petechiation, ecchymosis)
  • Normal platelet count
115
Q

Are platelet qualitative disorders acquired, inherited or can be both?

A

Can be both.

116
Q

What are 4 examples of causes of acquired platelet qualitative disorders?

A
  • Uremia
  • Drugs
  • Fibrin degradation products (FDPs)
  • Paraproteins
117
Q

What are 7 examples of drugs that can cause platelet qualitative disorders?

A
  • Aspirin
  • Phenylbutazone
  • Acetaminophen
  • NSAIDs
  • Some anesthetics
  • Xanthine derivatives
  • Calcium channel blockers
118
Q

What can inhibit platelet function in disease processes?

A

Fibrin degradation products (FDPs)

119
Q

What causes paraproteins?

How does this effect the platelets?

A
  • Plasma cell myeloma

- Increased globulins coat platelet surface and inhibits function.

120
Q

What are 4 examples of inherited causes of platelet qualitative disorders?

A
  • Absence of glycoprotein receptors
  • Absence or reduction in platelet granules
  • Signal transduction defect
  • von Willebrand’s disease
121
Q

What are 3 aspects of von Willebrand’s disease?

Which one is the most significant?

A
  • No defects in platelets
  • Defects is in the adhesion molecule that binds platelets during initiation of platelet plug
  • Decreased platelet adhesion (most significant)
122
Q

What are 2 things that happen with von Willebrand’s disease?

A
  • Platelets float away

- Platelet plug not formed

123
Q

Von Willebrand’s disease leads to what?

A

Decreased platelet adhesion

124
Q

What are the 2 forms of von Willebrand’s?

A
  • Quantitative deficiency (Types 1 and 3)

- Qualitative abnormality (Type 2)

125
Q

Is quantitative deficiency Type 1 von Willebrand’s disease mild or severe?
Type 3?

A
  • Type 1: mild, dogs usually subclinical

- Type 3 : severe

126
Q

Which factor is vWF a carrier for?

A

Factor VIII

127
Q

What is the major clinical feature seen with von Willebrand’s disease?
What is this exacerbated by?
Does this increase or decrease with age? Successive pregnancies?

A
  • Mild to severe bleeding
  • Surgery or trauma
  • Decrease, decrease
128
Q

Diagnosis of von Willebrand’s is based on what 4 factors?

A
  • Based on signalment
  • History
  • Medications
  • Other primary disorders
129
Q

How does the platelet count appear with von Willebrand’s disease?

A

Normal platelet count

130
Q

What is seen with the buccal mucosal bleeding time with von Willebrand’s disease?

A

Prolonged BMBT

131
Q

If vWD is suspected, analyze the plasma for what?

A

vWF

132
Q

What effect does vWD have on PTT/ACT?

What is an exception?

A
  • Both usually normal

- Both can be prolonged if Factor VIII deficiency is pronounced

133
Q

What is B1-tubulin gene mutation?

What breed is it seen in?

A
  • Point mutation that alters the cytoskeleton

- Cavalier King Charles Spaniels

134
Q

What 2 things does the B1-tubulin gene mutation cause?

A
  • Decreased platelet count

- Increased platelet MCV (macrothrombocytes)

135
Q

T/F: B1-tubulin gene mutation is usually asymptomatic.

A

True

136
Q

What are 4 examples of lab diagnostics for platelets and what do they measure?

A
  • Blood smears: estimate of platelet numbers, morphology (size)
  • Analyzers: platelet counts and MPV
  • Bleeding tests: platelet function
  • Bone marrow aspirates: platelet production
137
Q

What are 4 major categories of thrombocytopenia causes?

A
  • Loss, consumption
  • Destruction
  • Production
  • Sequestration
138
Q

What do the offspring ingest with alloimmune thrombocytopenia?

A

Antibody in the colostrum.

139
Q

Piglets with alloimmune thrombocytopenia have a high mortality rate from what?

A

Hemorrhage

140
Q

What type of vaccination may induce an immune response against the platelets, leading to platelet aggregation and clearance?

A

Modified-live virus vaccination

141
Q

Thrombocytopenia due to vaccination usually occurs when?

A

3-10 days post-vaccination

142
Q

Is thrombocytopenia seen with vaccines usually mild or severe?

A

Mild

143
Q

A complete blood count (CBC) can detect what type of thrombocytopenia?

A

Severe thrombocytopenia

144
Q

Bone marrow aspirates are used to detect what?

A

Increased megakaryocytes (immature & mature)

145
Q

What are 3 possible causes of decreased production of platelets?

A
  • Bone marrow hypoplasia
  • Neoplasia
  • Myelonecrosis or myelofibrosis
146
Q

The degree of thrombocytopenia seen with decreased production depends on what?

A

Extent of bone marrow disease.

147
Q

What is the most common form of abnormal distribution of platelets?

A

Sequestration of platelets in large vascular beds.

148
Q

What level of thrombocytopenia is seen with abnormal distribution of platelets?

A

Mild to moderate thrombocytopenia

149
Q

What are 2 possible reason an analyzer might not measure platelets, leading to pseudothrombocytopenia?

A
  • Too big (macrothrombocytes)

- Clumped

150
Q

An increased concentration of platelets is known as what?

A

Thrombocytosis

151
Q

What are 2 major mechanisms of thrombocytosis?

A
  • Increased production

- Increased distribution in plasma

152
Q

What type of symptoms are usually seen in animals with an increased platelet count?

A

Animals are usually asymptomatic.

153
Q

What are 2 possible reasons for increased concentration of platelets?
Which one is more common?

A
  • Primary neoplastic production of platelets

- Secondary or reactive thrombocytosis (more common)

154
Q

What are 5 possible causes of secondary or reactive thrombocytosis?
Which is the most common?

A
  • Chronic inflammatory disease (most common)
  • Iron deficiency anemia
  • Chronic hemorrhage
  • IMHA
  • Some neoplasms
155
Q

Increased concentration of platelets can be associated with what 4 situations?

A
  • Rebound from thrombocytopenia
  • Post-splenectomy
  • Response to some drugs (vincristine)
  • Excitement and exercise (epinephrine)
156
Q

Platelet qualitative disorders may be suspected in animals with what 2 conditions?

A
  • Clinical signs of thrombocytopenia (mucosal bleeding, petechiation, ecchymosis)
  • Normal platelet count
157
Q

Are platelet qualitative disorders acquired, inherited or can be both?

A

Can be both.

158
Q

What are 4 examples of causes of acquired platelet qualitative disorders?

A
  • Uremia
  • Drugs
  • Fibrin degradation products (FDPs)
  • Paraproteins
159
Q

What are 7 examples of drugs that can cause platelet qualitative disorders?

A
  • Aspirin
  • Phenylbutazone
  • Acetaminophen
  • NSAIDs
  • Some anesthetics
  • Xanthine derivatives
  • Calcium channel blockers
160
Q

What can inhibit platelet function in disease processes?

A

Fibrin degradation products (FDPs)

161
Q

What causes paraproteins?

How does this effect the platelets?

A
  • Plasma cell myeloma

- Increased globulins coat platelet surface and inhibits function.

162
Q

What are 4 examples of inherited causes of platelet qualitative disorders?

A
  • Absence of glycoprotein receptors
  • Absence or reduction in platelet granules
  • Signal transduction defect
  • von Willebrand’s disease
163
Q

What are 3 aspects of von Willebrand’s disease?

Which one is the most significant?

A
  • No defects in platelets
  • Defects is in the adhesion molecule that binds platelets during initiation of platelet plug
  • Decreased platelet adhesion (most significant)
164
Q

What are 2 things that happen with von Willebrand’s disease?

A
  • Platelets float away

- Platelet plug not formed

165
Q

Von Willebrand’s disease leads to what?

A

Decreased platelet adhesion

166
Q

What are the 2 forms of von Willebrand’s?

A
  • Quantitative deficiency (Types 1 and 3)

- Qualitative abnormality (Type 2)

167
Q

Is quantitative deficiency Type 1 von Willebrand’s disease mild or severe?
Type 3?

A
  • Type 1: mild, dogs usually subclinical

- Type 3 : severe

168
Q

Which factor is vWF a carrier for?

A

Factor VIII

169
Q

What is the major clinical feature seen with von Willebrand’s disease?
What is this exacerbated by?
Does this increase or decrease with age? Successive pregnancies?

A
  • Mild to severe bleeding
  • Surgery or trauma
  • Decrease, decrease
170
Q

Diagnosis of von Willebrand’s is based on what 4 factors?

A
  • Based on signalment
  • History
  • Medications
  • Other primary disorders
171
Q

How does the platelet count appear with von Willebrand’s disease?

A

Normal platelet count

172
Q

What is seen with the buccal mucosal bleeding time with von Willebrand’s disease?

A

Prolonged BMBT

173
Q

If vWD is suspected, analyze the plasma for what?

A

vWF

174
Q

What effect does vWD have on PTT/ACT?

What is an exception?

A
  • Both usually normal

- Both can be prolonged if Factor VIII deficiency is pronounced

175
Q

What is B1-tubulin gene mutation?

What breed is it seen in?

A
  • Point mutation that alters the cytoskeleton

- Cavalier King Charles Spaniels

176
Q

What 2 things does the B1-tubulin gene mutation cause?

A
  • Decreased platelet count

- Increased platelet MCV (macrothrombocytes)

177
Q

T/F: B1-tubulin gene mutation is usually asymptomatic.

A

True

178
Q

What are 4 examples of lab diagnostics for platelets and what do they measure?

A
  • Blood smears: estimate of platelet numbers, morphology (size)
  • Analyzers: platelet counts and MPV
  • Bleeding tests: platelet function
  • Bone marrow aspirates: platelet production
179
Q

What are 4 major categories of thrombocytopenia causes?

A
  • Loss, consumption
  • Destruction
  • Production
  • Sequestration

Clinical Pathology (12 decks)

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