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Haematology & haematopoeisis Flashcards

(102 cards)

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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
What different kinds of pool are created by granulocytopoeisis?
Proliferative pool - 20-25% of all granulocytes Maturation pool - e.g. band neutrophils Storage pool - segmented neutrophils
26
Within homeostasis, what kinds of neutrophils are seen within the circulation?
Mature
27
In what instance might earlier stages of neutrophils be released? What is the term for this occurrence?
During a severe inflammation A left shift
28
With regards to neutrophil production, what does inflammation induce?
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
29
What roles does cytokine interleukin-5 play in eosinopoeisis?
Growth Differentiation Activation
30
How frequently are mast cells seen in circulation? In what instances might they be seen in cats, dogs or horses?
Very rarely seen in circulation Seen in dogs + horses with inflammation or trauma Seen in cats most often with neoplasia
31
State 6 important minerals + vitamins considered essential for erythropoiesis.
Fe Cu Vit B2 Vit B6 Vit B12 Folate
32
What is the clinical significance of RBC release?
Efficiency in increasing output of RBC if needed Increased % of immature RBC in circulation Lag-time
33
Describe the process of erythropoeisis.
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
34
What is the name of the latest stage of nucleated erythrocyte? Describe this stage.
Metarubricyte or normoblast nRBC are not seen in circulation unless erythropoeisis is accelerated or bone marrow is damaged
35
What does the presence of juvenile RBCs indicate? Describe juvenile RBCs.
Regeneration + accelerated erythropoeisis Blueish appearance in routing stains, or as reticulocytes in supravital stains
36
What route are reticulocytes known to take as part of erythrocyte release?
Migrate through transient aperture in endothelial cell to reach venous sinuses
37
What is the role of the spleen in relation to juvenile reticulocytes? In which species is this known to be less effective?
Spleen pits organelles Less effective in cats ⇒ organelles may be present for longer
38
What type of stain is used for reticulocyte identification + enumeration?
Methylene blue stain
39
What does endomitosis mean? What does this process produce?
Nuclear division but no cellular division Produces megakaryoblasts → megakaryocytes
40
Which organ produces thrombocytes? What hormone regulates this process?
Liver constantly produces thrombocytes Regulated by thrombopoeitin
41
What 2 exceptions affect thrombopoeisis?
IL-6 -produced in response to inflammation - can increased thrombopooeitin synthesis independently of platelet numbers Fe deficiency also causes thrombopoeisis independently of thrombpoeitin
42
What does haematology study?
Changes in cellular components
43
What is the opposing process to erythrocytosis?
Anaemia
44
What does pancytopaenia mean?
Describes a situation in which all 3 elements of the blood are decreased: anaemia, leucopaenia + thrombocytopaenia
45
What means are there for detecting blood abnormalities?
Suspicions based on clinical signs - pallor, exercise intolerance, bleeding, pyrexia Confirmation with laboratory tests
46
What different laboratory tests are there?
Centrifugation of microhaematocrit tubes Blood counts Blood smear evaluation
47
What should a complete haemogram be comprised of?
Centrifugation of microhaematocrit tube Blood count Blood smear
48
What tests constitute the minimum database for emergency setting?
Blood smear PCV/TP
49
What sample is ideal for a haemogram?
Blood in EDTA tube - anticoagulated whole blood
50
What needs to be avoided when processing haematology samples?
Avoid: inadequate mixing of specimens Haemolysed specimens Lipaemic (fatty) specimens - by fasting Clotted specimens Platelet clumps Diluted specimens
51
What features are there in a haemogram?
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
What is MCV?
Mean corpuscular volume - average RBC size
53
What does MCHC stand for?
Mean corpuscolar Hb concentration - average RBC Hb conc
54
What does MCH refer to?
Mean corpuscolar Hb - average erythrocyte Hb per cell
55
What does a raised MCV (mean corpuscolar volume) mean?
Macrocytic anaemia - presence of larger cells, that are usually juvenile RBCs - likely to be regenerative anaemia
56
If MCV is normal, how is this described?
Normocytic anaemia - non-regenerative though might be regenerative
57
How would microcytic anaemia be detected?
As reduced MCV - production of small RBCs, likely due to less Hb available for erythropoeisis caused by Fe deficiency
58
What does normochromic anaemia refer to?
When MCHC (mean corpuscolar Hb concentration) is normal - usually non-regenerative, though still might be regenerative
59
What happens when MCHC is reduced?
Hypochromic anaemia is seen With regeneration (juvenile RBCs) or Fe deficiency
60
What is the most likely explanation for a raised MCHC?
Almost always artefactual
61
What means are there for assessing regeneration?
Bone marrow exam - most sensitive; invasive + expensive Enumeration of reticulocytes - absolute count is most useful
62
How is renumeration of reticulocytes calculated?
%reticulocytes x RBC x 10 = absolute reticulocyte count
63
At what absolute counts are reticulocytes considered to be non-regenerative?
\<60 reticulocytes 109/L in dogs \<40 reticulocytes 109/L in cats
64
What is the term for abnormal RBC shape?
Poikilocytosis
65
What can cause a state of regenerative anaemia?
Blood loss Haemolysis (increased RBC destruction)
66
What could decreased erythrocyte production result in?
Non-regenerative anaemia
67
What happens in a state of regenerative anaemia?
Bone marrow responds to decreased O2 carrying capacity by increasing erythropoiesis Results in higher numbers of juvenile RBC in circulation
68
What happens in a state of non-regenerative anaemia?
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
Describe blood loss anaemia.
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
Describe the state of acute blood loss.
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
Describe the state of chronic blood loss.
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
What different types of haemolysis are there? State the causes.
**Immune-mediated:** - immune-mediated haemolysis **Non immune-mediated:** - oxidative damage - intra-erythrocytic parasites - bacteria + viruses - mechanical damage
73
What is partial phagocytosis? What does it commonly occur in conjunction with?
Often alongside immune-mediated haemolysis Macrophages pit membrane portion with ag-ab complex → decreased RBC surface → loss of discoid shape ⇒ **spherocyte**
74
What does the occurrence of many spherocytes indicate?
Strongly supportive of immune-mediated haemolytic anaemia
75
What is a supporting factor for the occurrence of immune-mediated haemolytic anaemia?
Agglutination
76
What is agglutination? What does it bear close resemblance to?
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
Why might anaemia develop?
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
When classifying anaemia, what should be assessed?
Degree of severity: mild, moderate, severe Erythrocyte indexes: MCV, MCHC Regenerative response Pathophysiologic mechanism: haeme findings, clinical signs, TP, plasma colour
79
What does neutrophilia refer to?
Neutrophil count above the upper reference limit
80
What could potentially cause neutrophilia?
Inflammation: chronic or acute
81
What does neutropaenia refer to?
Neutrophil count being below the upper reference limit
82
What potential causes are there for neutropaenia?
Severe overwhelming inflammation Bone marrow disease
83
What does a left shift refer to?
Number of juvenile RBCs above the upper reference level
84
In what instance is a left shift normally seen?
Usually severe inflammation - bacterial infection, immune-mediated disease
85
In what circumstances might monocytosis be seen?
Chronic inflammation Tissue damage Necrosis
86
When might lymphocytosis be seen?
Chronic inflammation Adrenaline release in cats → splenic contraction → increased circulating lymphocytes
87
How can immature neutrophils be detected?
Their C-shaped nucleus
88
What are platelets?
Cytoplasmic fragments of megakaryocytes derived from pluripotent hernatpoeitic cells in the bone marrow
89
Which organ harbours 1/3 of platelets?
Spleen
90
What does splenic contraction result in?
Platelet mobilisation
91
In which species are giant platelets a common finding in healthy individuals?
Healthy cats
92
What do increased numbers of giant platelets indicate?
Increased thrombopoeisis
93
In which species are platelet clumps most common?
Bovine + feline samples
94
What causes are there for thrombocytopaenia?
Increased destruction Increased consumption Decreased production Redistribution/sequestration
95
What does destruction thrombocytopaenia refer to?
Immune-mediated thrombocytopaenia - autoimmune/idiopathic - drug reactions - triggered by infectious diseases or neoplasia
96
What does consumption thrombocytopaenia refer to?
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
With both consumption + destruction thrombocytopaenias, how well does bone marrow function? What kind of anaemia is seen?
No marrow problems - fully functioning Larger platelets are seen
98
What happens with decreased production of thrombocytes?
Destruction of megakaryocytes in bone marrow - either decreased or absent
99
What does distributional thrombocytopaenia refer to?
Splenomegaly - splenic torsion Severe hypothermia Endotoxaemia
100
What mechanisms prompt thrombocytosis?
Excitement Post-splenectomy Chronic bleeding Fe deficiency Inflammation: IL-6 → thrombopoeitin Neoplasia of megakaryocytes
101
State 6 clinical signs of defects in primary haemostasis.
- petechiae - ecchymoses - epistaxis - melena - haematochezia - haematuria
102

Pathology (7 decks)

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