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Pathology > Haematology & haematopoeisis > Flashcards

Haematology & haematopoeisis Flashcards

1
Q

What is the function of RBCs?

A

To transport O2 via Hb from lungs ⇒ peripheral tissues

And CO2 back to lungs - Hb + HCO3-

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2
Q

Name 2 roles carried out by WBCs.

A

Destruction of microorganisms

Removal of dead or damaged tissues

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3
Q

What is the biological significance of platelets? What are they also known as?

A

Haemostasis

Thrombocytes

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4
Q

State 3 different functions of plasma.

A
  1. Carries nutrients + waste products
  2. Clotting + maintenance of fluidity
  3. Intravascular oncotic pressure
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5
Q

What are the different lifespans for the components of blood?

A

RBCs - 1 to >5mo

WBC: lymphocytes - weeks-years

monocytes - days (then transform into macrophages)

neutrophils - 10hrs in blood; 24-48hrs in tissues

Platelets - 10d

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6
Q
A
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7
Q

Which type of blood cells transform into macrophages?

A

Monocytes

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8
Q

What is the term for a reduction in the number of neutrophils?

A

Neutropaenia

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9
Q

Describe the process for breakdown of old RBCs.

A

RBCs are consumed by macrophages and lysed

Producing AAs - return to circulation

Fe2+ - returns to blood as transferrin + stored as ferritin in liver or used to produce more RBCs in bone marrow

bilirubin - re-enters circulation to be excreted by liver as bile

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10
Q

By what routes are blood components lost?

A

Cell ageing or damage

Pathologic, haemorrhage or parasitic loss

Pathologic increased destruction

Consumption - platelets within clots

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11
Q

What colour does hyperbilirubinaemia induce in plasma?

A

Yellow discolouration

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12
Q

What is haemoglobinuria? How is it detected?

A

Excretion of free Hb in urine

This causes red urine to be produced

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13
Q

What processes produce more blood components?

A

Haemopoeisis

Protein synthesis by liver + immune system

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14
Q

What is meant by haemopoeitic tissue?

A

Haematopoeitic islands in yolk sac + aorta-gonad-mesonephros of embryo

Bone marrow

Extramarrow sites: liver, spleen, kidney (fish + amphibians)

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15
Q

What is yellow marrow?

A

Bone marrow mainly composed of adipose cells that can be converted to haemopoeitic lines if necessary

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16
Q

What is the original cell within the haematopoeitic hierachy?

A

Pluripotent stem cells

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17
Q

Describe a pluripotent stem cell.

A

Common precursor for all cells

Found scattered throughout bone marrow

Appearance - like a small lymphocyte

Influenced by cytokines, growth factors + hormones

Able to self-renew + produce more commited stem cells

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18
Q

Give 2 examples of committed progenitor cells. Describe their cell renewing abilities.

A

Myeloid stem cell

Lymphoid stem cell

Incapable of self-renewal

Proliferate when differentiating into mature cells → pyramidal expansion

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19
Q

What is lymphogenesis? Where does this process occur?

A

Process of producing lymphocyte cells

In the lymphoid organs - bone marrow + thymus

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20
Q

Describe lymphocytes with regards to lymphogenesis.

A

Most later stages of lymphocytes form in the lymphoid organs

Lymphocytes can recirculate + maintain a ‘memory’ of ag encountered

With immune stimulation, mature lymphocytes may still undero mitosis → larger reactive forms

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21
Q

What are CFUs? What is their haematological significance?

A

Colony forming units

Develop from committed stem cells

Give rise to different types of blast which will eventually evolve into mature cells

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22
Q

What is myelopoeisis?

A

Production of blood cells with the exception of neutrophils.

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23
Q

What is the term for production of granulocytes aka polymorphonuclears (neutrophils, eosinophils, basophils) and monocytes?

A

Granulopoeisis

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24
Q

What is the differentiation of the products of granulopoeisis controlled by?

A

Colony stimulating factors = cytokines, e.g. IL-3

several growth factors

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25
Q

What different kinds of pool are created by granulocytopoeisis?

A

Proliferative pool - 20-25% of all granulocytes

Maturation pool - e.g. band neutrophils

Storage pool - segmented neutrophils

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26
Q

Within homeostasis, what kinds of neutrophils are seen within the circulation?

A

Mature

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27
Q

In what instance might earlier stages of neutrophils be released? What is the term for this occurrence?

A

During a severe inflammation

A left shift

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28
Q

With regards to neutrophil production, what does inflammation induce?

A

May caused neutrophilia due to release from storage pool + myelopoeisis

If very acute + severe (overwhelming), may cause neutropaenia due to consumption of circulating + stored neutrophils

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29
Q

What roles does cytokine interleukin-5 play in eosinopoeisis?

A

Growth

Differentiation

Activation

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30
Q

How frequently are mast cells seen in circulation? In what instances might they be seen in cats, dogs or horses?

A

Very rarely seen in circulation

Seen in dogs + horses with inflammation or trauma

Seen in cats most often with neoplasia

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31
Q

State 6 important minerals + vitamins considered essential for erythropoiesis.

A

Fe

Cu

Vit B2

Vit B6

Vit B12

Folate

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32
Q

What is the clinical significance of RBC release?

A

Efficiency in increasing output of RBC if needed

Increased % of immature RBC in circulation

Lag-time

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33
Q

Describe the process of erythropoeisis.

A

Large blast cells divide + become smaller

Hb concentration increases

Cell division stops when optimal IC Hb conc is reached

Nucleus is extruded

Organelles + RNA are progressively lost

Mature RBC only contain Hb = pink colour

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34
Q

What is the name of the latest stage of nucleated erythrocyte? Describe this stage.

A

Metarubricyte or normoblast

nRBC are not seen in circulation unless erythropoeisis is accelerated or bone marrow is damaged

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35
Q

What does the presence of juvenile RBCs indicate? Describe juvenile RBCs.

A

Regeneration + accelerated erythropoeisis

Blueish appearance in routing stains, or as reticulocytes in supravital stains

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36
Q

What route are reticulocytes known to take as part of erythrocyte release?

A

Migrate through transient aperture in endothelial cell to reach venous sinuses

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37
Q

What is the role of the spleen in relation to juvenile reticulocytes? In which species is this known to be less effective?

A

Spleen pits organelles

Less effective in cats ⇒ organelles may be present for longer

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38
Q

What type of stain is used for reticulocyte identification + enumeration?

A

Methylene blue stain

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39
Q

What does endomitosis mean? What does this process produce?

A

Nuclear division but no cellular division

Produces megakaryoblasts → megakaryocytes

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40
Q

Which organ produces thrombocytes? What hormone regulates this process?

A

Liver constantly produces thrombocytes

Regulated by thrombopoeitin

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41
Q

What 2 exceptions affect thrombopoeisis?

A

IL-6 -produced in response to inflammation - can increased thrombopooeitin synthesis independently of platelet numbers

Fe deficiency also causes thrombopoeisis independently of thrombpoeitin

42
Q

What does haematology study?

A

Changes in cellular components

43
Q

What is the opposing process to erythrocytosis?

A

Anaemia

44
Q

What does pancytopaenia mean?

A

Describes a situation in which all 3 elements of the blood are decreased: anaemia, leucopaenia + thrombocytopaenia

45
Q

What means are there for detecting blood abnormalities?

A

Suspicions based on clinical signs - pallor, exercise intolerance, bleeding, pyrexia

Confirmation with laboratory tests

46
Q

What different laboratory tests are there?

A

Centrifugation of microhaematocrit tubes

Blood counts

Blood smear evaluation

47
Q

What should a complete haemogram be comprised of?

A

Centrifugation of microhaematocrit tube

Blood count

Blood smear

48
Q

What tests constitute the minimum database for emergency setting?

A

Blood smear

PCV/TP

49
Q

What sample is ideal for a haemogram?

A

Blood in EDTA tube - anticoagulated whole blood

50
Q

What needs to be avoided when processing haematology samples?

A

Avoid: inadequate mixing of specimens

Haemolysed specimens

Lipaemic (fatty) specimens - by fasting

Clotted specimens

Platelet clumps

Diluted specimens

51
Q

What features are there in a haemogram?

A

Total Hb content

Haematocrit - equivalent to PCV

RBC count

RBC indexes: MCV, MCHC, MCH

Total WBC count

Differential WBC counts

Platelet count

Reticulocyte count

52
Q

What is MCV?

A

Mean corpuscular volume - average RBC size

53
Q

What does MCHC stand for?

A

Mean corpuscolar Hb concentration - average RBC Hb conc

54
Q

What does MCH refer to?

A

Mean corpuscolar Hb - average erythrocyte Hb per cell

55
Q

What does a raised MCV (mean corpuscolar volume) mean?

A

Macrocytic anaemia - presence of larger cells, that are usually juvenile RBCs

  • likely to be regenerative anaemia
56
Q

If MCV is normal, how is this described?

A

Normocytic anaemia - non-regenerative though might be regenerative

57
Q

How would microcytic anaemia be detected?

A

As reduced MCV - production of small RBCs, likely due to less Hb available for erythropoeisis caused by Fe deficiency

58
Q

What does normochromic anaemia refer to?

A

When MCHC (mean corpuscolar Hb concentration) is normal

  • usually non-regenerative, though still might be regenerative
59
Q

What happens when MCHC is reduced?

A

Hypochromic anaemia is seen

With regeneration (juvenile RBCs) or Fe deficiency

60
Q

What is the most likely explanation for a raised MCHC?

A

Almost always artefactual

61
Q

What means are there for assessing regeneration?

A

Bone marrow exam - most sensitive; invasive + expensive

Enumeration of reticulocytes - absolute count is most useful

62
Q

How is renumeration of reticulocytes calculated?

A

%reticulocytes x RBC x 10 = absolute reticulocyte count

63
Q

At what absolute counts are reticulocytes considered to be non-regenerative?

A

<60 reticulocytes 109/L in dogs

<40 reticulocytes 109/L in cats

64
Q

What is the term for abnormal RBC shape?

A

Poikilocytosis

65
Q

What can cause a state of regenerative anaemia?

A

Blood loss

Haemolysis (increased RBC destruction)

66
Q

What could decreased erythrocyte production result in?

A

Non-regenerative anaemia

67
Q

What happens in a state of regenerative anaemia?

A

Bone marrow responds to decreased O2 carrying capacity by increasing erythropoiesis

Results in higher numbers of juvenile RBC in circulation

68
Q

What happens in a state of non-regenerative anaemia?

A

Bone marrow is unable to respond to either 1º bone marrow disease or it does not sense decreased O2 carrying capacity

e.g. failure of kidneys to produce erythrpoietin

69
Q

Describe blood loss anaemia.

A

Can be acute or chronic

= proportional loss of all blood components

  1. Initial decrease of blood volume
  2. Within a few hours, activation of mechanisms to maintain volaemia → influx of H2O from EC space → dilution → reduction of haematocrit + TP

Causes: haemorrhage, blood-sucking parasites

70
Q

Describe the state of acute blood loss.

A

Usually bone marrow is able to compensate for loss by increasing erythropoeisis

Red cell mass will normalise in 1-2wks

  • decreased TP is expected
  • evidence of regeneration - erythroid hyperplasia in bone marrow
  • reticulocytosis/polychromasia in blood
71
Q

Describe the state of chronic blood loss.

A

Gastrointestinal bleeding is most common cause

Refers to bleeding for >2wks

May lead to consumption of Fe stores + Fe deficiency anemia (IDA)

May be regenerative/non-regenerative - eventually Fe deplection will slow down erythropoeisis

72
Q

What different types of haemolysis are there? State the causes.

A

Immune-mediated:

  • immune-mediated haemolysis

Non immune-mediated:

  • oxidative damage
  • intra-erythrocytic parasites
  • bacteria + viruses
  • mechanical damage
73
Q

What is partial phagocytosis? What does it commonly occur in conjunction with?

A

Often alongside immune-mediated haemolysis

Macrophages pit membrane portion with ag-ab complex → decreased RBC surface → loss of discoid shape ⇒ spherocyte

74
Q

What does the occurrence of many spherocytes indicate?

A

Strongly supportive of immune-mediated haemolytic anaemia

75
Q

What is a supporting factor for the occurrence of immune-mediated haemolytic anaemia?

A

Agglutination

76
Q

What is agglutination? What does it bear close resemblance to?

A

Ab-mediated clumping of RBC - may be temperature dependent

* strongly supportive of IMHA

Sometimes difficult to distinguish from Rouleaux formation = stacking of RBC due to increased plasma proteins coating them

  • can be caused by inflammation, cancer
  • normal occurrence in horses + cats
77
Q

Why might anaemia develop?

A

Decreased erythropoietin - anaemia develops because bone marrow doesn’t replace daily RBC loss

Caused by:

  • 1º bone marrow disease
  • lack of erythropoeitin
  • altered microenvironment - lack of vits, Fe
  • chronic inflammation
78
Q

When classifying anaemia, what should be assessed?

A

Degree of severity: mild, moderate, severe

Erythrocyte indexes: MCV, MCHC

Regenerative response

Pathophysiologic mechanism: haeme findings, clinical signs, TP, plasma colour

79
Q

What does neutrophilia refer to?

A

Neutrophil count above the upper reference limit

80
Q

What could potentially cause neutrophilia?

A

Inflammation: chronic or acute

81
Q

What does neutropaenia refer to?

A

Neutrophil count being below the upper reference limit

82
Q

What potential causes are there for neutropaenia?

A

Severe overwhelming inflammation

Bone marrow disease

83
Q

What does a left shift refer to?

A

Number of juvenile RBCs above the upper reference level

84
Q

In what instance is a left shift normally seen?

A

Usually severe inflammation - bacterial infection, immune-mediated disease

85
Q

In what circumstances might monocytosis be seen?

A

Chronic inflammation

Tissue damage

Necrosis

86
Q

When might lymphocytosis be seen?

A

Chronic inflammation

Adrenaline release in cats → splenic contraction → increased circulating lymphocytes

87
Q

How can immature neutrophils be detected?

A

Their C-shaped nucleus

88
Q

What are platelets?

A

Cytoplasmic fragments of megakaryocytes derived from pluripotent hernatpoeitic cells in the bone marrow

89
Q

Which organ harbours 1/3 of platelets?

A

Spleen

90
Q

What does splenic contraction result in?

A

Platelet mobilisation

91
Q

In which species are giant platelets a common finding in healthy individuals?

A

Healthy cats

92
Q

What do increased numbers of giant platelets indicate?

A

Increased thrombopoeisis

93
Q

In which species are platelet clumps most common?

A

Bovine + feline samples

94
Q

What causes are there for thrombocytopaenia?

A

Increased destruction

Increased consumption

Decreased production

Redistribution/sequestration

95
Q

What does destruction thrombocytopaenia refer to?

A

Immune-mediated thrombocytopaenia

  • autoimmune/idiopathic
  • drug reactions
  • triggered by infectious diseases or neoplasia
96
Q

What does consumption thrombocytopaenia refer to?

A

Intravascular coagulation

  • disseminated intravascular coagulation (DIC)
  • vascular neoplasia, thrombosis

Inflammation of vessels

  • heart worm disease, bacterial infection

Acute + severe blood loss

  • only if very acute + massive otherwise platelet mobilisation from spleen is sufficient to compensate
97
Q

With both consumption + destruction thrombocytopaenias, how well does bone marrow function? What kind of anaemia is seen?

A

No marrow problems - fully functioning

Larger platelets are seen

98
Q

What happens with decreased production of thrombocytes?

A

Destruction of megakaryocytes in bone marrow

  • either decreased or absent
99
Q

What does distributional thrombocytopaenia refer to?

A

Splenomegaly - splenic torsion

Severe hypothermia

Endotoxaemia

100
Q

What mechanisms prompt thrombocytosis?

A

Excitement

Post-splenectomy

Chronic bleeding

Fe deficiency

Inflammation: IL-6 → thrombopoeitin

Neoplasia of megakaryocytes

101
Q

State 6 clinical signs of defects in primary haemostasis.

A
  • petechiae
  • ecchymoses
  • epistaxis
  • melena
  • haematochezia
  • haematuria
102
Q
A

Pathology (7 decks)

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