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Y2 Clinical Pathology > Introduction to Haematology > Flashcards

Introduction to Haematology Flashcards

1
Q

What is the definition of haematology?

A

Biology and pathology of the cells that normally circulate in the blood 🩸

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2
Q

What is the definition of haemopoiesis?

A

The physiological developmental process that gives rise to the cellular components of the blood

a single multipotent haemopoietic stem cell can divide and differentiate to form different cell lineages that will populate the blood

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3
Q

What is the difference between symmetrical and asymmetrical division when the haemopoietic stem cell undergoes differentiation and/or self-renewal?

A

Symmetrical division:

  • may yield two identical stem cells
  • or two daughter cells that have undergone a degree of differentiation and concomitant loss of self-renewal capacity

Aysmmetrical division:

  • both a stem cell and a daughter cell are generated
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4
Q

What are the 2 different types of symmetrical division?

A

Symmetric self-renewal:

  • increase stem cell pool
  • no generation of differentiated progeny

Lack of self-renewal:

  • depletion of stem cell pool
  • generation of differentiated progeny ONLY
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5
Q

What is meant by aysmmetric self-renewal and lack of self-renewal?

A

Asymmetric self-renewal:

  • maintains the stem cell pool
  • generation of differentiated progeny

Lack of self-renewal:

  • maintain the stem cell pool
  • no differentiated progeny
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6
Q

What are the characteristics of the haemopoietic stem cell?

A
  1. Self-renewal
  2. High proliferative potential
  3. Differentiation potential for all lineages
  4. Long term activity throughout the lifespan of the individual
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7
Q

What is an example that gives experimental proof of the properties of the haemopoietic stem cell?

A
  • Stem cells transplanted from one mouse to another over several generations
  • bone marrow transplantation in humans
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8
Q

What are the 2 different haemopoietic lineages with examples?

A

Myeloid:

  • granulocytes (white blood cells)
  • erythrocytes (red blood cells)
  • platelets

Lymphoid:

  • B-lymphocytes
  • T-lymphocytes
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9
Q

How do stem cells help to maintain the cellular content of the blood?

A

Stem cells give rise to sufficient numbers of committed haemopoietic progenitors to maintain the cellular content of the blood throughout the lifespan of the individual

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10
Q

What are the stages shown in haemopoiesis?

A
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11
Q

What is the lifespan of an erythrocyte and neutrophil like?

A

Mature blood cells all have a finite life

an erythrocyte has a lifespan of about 120 days

a neutrophil only lasts for 6-10 hours in the bloodstream

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12
Q

What is the difference between pluripotent and committed stem cells?

A

Pluripotent stem cells:

  • ​develop into cells and tissues of the three primary germ layers
  • can develop into any type of cell in the body

Committed stem cell:

  • cells that have been committed to a particular pathway of differentiation
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13
Q

Label the components of the trophoblast at 9 days

A

Extra-embryonic coelom is the chorionic cavity

this is a fluid-filled area formed from trophoblast and extra-embryonic mesoderm that forms the placenta

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14
Q

What is the morula?

A

An early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida

it goes on to form the blastula

trophoblasts are cells forming the outer layer of the blastocyst

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15
Q

When does haematopoiesis start?

Where does this occur?

A

Haemopoiesis starts at day 27 in the aorto-gonado-mesonephros

this expands rapidly at day 35, and then disappears at day 40

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16
Q

What happens when the aorto-gonado-mesonephros disappears at day 40?

A

The disappearance correlates with the migration of the haemopoietic stem cells to the foetal liver

this becomes the subsequent site of haemopoiesis

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17
Q

What are the 4 main functions of blood cells?

A
  • Oxygen transport
  • coagulation (haemostasis)
  • immune response to infection
  • immune response to abnormal cells (senescent, malignant, etc.)
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18
Q

What are the properties of erythrocytes?

How many are present in the body?

A

Biconcave discs that are 7.5 um in diameter

lifespan of 120 days in the blood

contain haemoglobin

there are 333,200 x 106 red cells in the blood

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19
Q

What is it called when there are reduced and raised red cells?

A

Anaemia occurs when there are reduced red cells

polycythaemia occurs when there are raised red cells

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20
Q

What is relative polycythaemia?

A

The number of red blood cells has not changed but the plasma volume has been reduced

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21
Q

What are the functions of white blood cells (leukocytes)?

What are the 3 different types?

A

They have functions in immunity and host defence

granulocytes:

  • have cytoplasmic granules
  • neutrophils, eosinophils, basophils

monocytes

lymphocytes

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22
Q

How many neutrophils are present in the blood usually?

A

They are phagocytes and the most common white cell in adult blood

10 x 109 per litre

they live for only a few hours in the blood

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23
Q

What is it called when there are increased and decreased numbers of neutrophils in the blood?

Why might this occur?

A

Neutrophilia:

  • increased numbers of neutrophils
  • occurs in bacterial infection and inflammation

Neutropenia:

  • decreased numbers of neutrophils
  • occurs as a side effect of some drugs
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24
Q

When might there be increased numbers of eosinophils?

A

Eosinophilia is an increase in the number of eosinophils

this occurs in allergies and parasitic infection

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25
Q

What is the role of basophils?

When may there be an increase in basophils and what is this called?

A

Basophils are rare cells that are part of the primitive immune system

basophilia is an increase in the number of basophils

this occurs in chronic myeloid leukaemia

26
Q

What are the roles of monocytes?

Where do they migrate to?

A

They are phagocytic and act as antigen-presenting cells

they migrate to tissues and are then identified as macrophages and histiocytes

e.g. Kupffer cells in the liver, Langerhans cells in the skin

27
Q

When may there be an increase in monocytes?

A

Monocytosis

this is an increase in the number of monocytes

occurs in tuberculosis

28
Q

What is it called when there is an increase or decrease in lymphocytes?

Why might this occur?

A

Lymphocytosis:

  • increase in number of lymphocytes
  • occurs in chronic lymphocytic leukaemia
  • atypical lymphocytes of glandular fever (infectious mononucleosis)

lymphopenia:

  • decrease in the number of lymphocytes
  • e.g. post bone marrow transplant
29
Q

What are the role of natural killer lymphocytes?

A

They are large granular lymphocytes that are part of the innate immune system

they recognise “non-self” - cells / viruses

30
Q

What are the roles of T-lymphocytes?

A

Part of the adaptive immune system

  • involved in cell-mediated immunity
  • target-specific cytotoxicity
  • interact with B cells and macrophages
  • regulate immune responses
31
Q

What are the roles of B-lymphocytes?

A

part of the adaptive immune system

  • rearrange immunoglobulin genes to enable antigen-specific antibody production
  • involved in humoral immunity
32
Q

What is plasmacytosis?

When may it occur?

A

An increase in the number of plasma cells (produced from B-lymphocytes)

occurs in infection and myeloma

33
Q

What are platelets formed from?

How many are present in the blood?

A

Platelets are derived from bone marrow megakaryocytes

there are 200 x 109 per litre

34
Q

What are the roles of platelets?

A

Together with soluble plasma clotting factors and endothelial cells, they form part of the blood clotting system

they aggregate to plug holes in damaged blood vessels

35
Q

What are the four main subdivisions of haematology clinical practice?

A
  • Coagulation
  • malignant
  • non-malignant
  • transfusion
36
Q

What diagnostic tests are used in haematology?

A
  • Full blood count
  • blood film (or “smear”)
  • coagulation screen
37
Q

What is involved in a full blood count?

A
  • Haemoglobin concentration
  • red cell parameters:

MCV - mean cell volume

MCH - mean cell Hb

  • white cell count (WCC)
  • platelet count
38
Q

What is a blood film?

A

A thin layer of blood smeared on a glass microscope slide and then stained in such a way as to allow the various blood cells to be examined microscopically

39
Q

What is a coagulation screen?

A

Tests that measure the time taken for a clot to form when plasma is mixed with specific reagents

various parts of the coagulation cascade can be assayed

40
Q

What types of things are looked at when a coagulation screen is performed?

A
  • Prothrombin time
  • activated partial thromboplastin time
  • thrombin time
41
Q

What is involved in a bone marrow aspirate & trephine?

A

Under local anaesthetic, liquid marrow is aspirated from the posterior iliac crest of the pelvis

a trephine core biopsy is then taken with a hollow needle

42
Q

What is a trephine?

A

A hole saw used in surgery to remove a circle of tissue or bone

43
Q

What is involved in obtaining a blood specimen?

A

An accurate FBC and correct interpretation of a blood film

  • need an appropriate sample from the patient
  • collect into EDTA anticoagulated blood

this should be mixed well and [K2EDTA] = 1.5 - 2.2 mg / ml

blood should be filled to the line on the tube

  • Samples should get to the lab promptly since EDTA artefact can affect the results
44
Q

What is EDTA and what does it do?

A

It is a chemical that binds and holds onto minerals and metals

e.g. Iron, lead, mercury, copper, magnesium, etc.

when they are bound, they cannot have any effects on the body and are removed from the body

45
Q

Why may test results vary?

A

Technical failure:

  • e.g. clotted sample or variation in reagents

normal variation:

  • intra-individual variation e.g. diurnal variation of cortisol levels
  • inter-individual variation e.g. platelet count

abnormal results

46
Q

How is a reference range established?

A

* Define the reference population

  • reference population should be relevant to the test population
  • consider if separate ranges are required for adults v children, men v women etc.
  • determine the expected range of inter individual variation
47
Q

What is meant by a reference range?

A

The set of values for a given test that incorporates 95% of the normal population

this is determined by collecting data from vast numbers of laboratory tests

95% of results should fall within the reference range

48
Q

What is shown in this image?

A

The distribution of test results for healthy and diseased subjects

TN - true negative

TP - true positive

FN - false negative

FP - false positive

49
Q

What is meant by sensitivity?

How is it calculated?

A

The proportion of abnormal results correctly classified by the test

expresses the ability to detect a true abnormality

sensitivity = TP / (TP + FN )

50
Q

What is the definition of specificity?

How is it calculated?

A

The proportion of normal results correctly classified by the test

expresses the ability to exclude an abnormal result in a healthy person

specificity = TN / (TN + FP )

51
Q

When interpreting full blood count, what is it important to keep in mind?

A

Be alert to technical problems:

  • e.g. thrombocytopenia is sometimes real and sometimes artefact

abnormal results:

  • will be flagged by the laboratory but may trigger additional tests e.g. blood film

serious urgent abnormalities:

  • laboratory staff will alert the on-call doctors e.g. new leukaemia
52
Q

Why is it important to know clinical details of patients when interpreting a full blood count?

A

FBC may fall outside the “normal range” but the results may be appropriate for the given clinical situation

e.g. Abnormal lymphocyte count

post-splenectomy mild lymphocytosis or 3 months post bone marrow transplant lymphopenia

53
Q

What are MCV and MCH in microcytic anaemia?

What are examples of microcytic anaemias?

A

MCV < 80 fl & MCH < 27 pg

  • iron deficiency
  • thalassaemia
  • anaemia of chronic disease (some)
  • lead poisoning
  • sideroblastic anaemia (some cases)
54
Q

What is meant by microcytic anaemia?

A

The presence of small, often hypochromic, red blood cells

55
Q

What are the MCV and MCH in normocytic normochromic anaemia?

What are examples of anaemias in this category?

A

MCV 80-95 fl & MCH >/= 27 pg

  • many haemolytic anaemias
  • anaemia of chronic disease (some cases)
  • after acute blood loss
  • renal disease
  • mixed deficiencies
  • bone marrow failure (e.g. post-chemotherapy, infiltration by carcinoma)
56
Q

What is meant by normocytic normochromic anaemia?

A

Anaemia in which the average size and haemoglobin content of the red blood cells are within normal limits

under the microscope, the cells resemble normal erythrocytes

57
Q

What is MCV in macrocytic anaemia?

What are the 2 different types?

A

MCV > 95 fl

megaloblastic:

  • vitamin B12 or folate deficiency

non-megaloblastic:

  • ​alcohol
  • liver disease
  • myelodysplasia
  • aplastic anaemia
58
Q

What is meant by macrocytic anaemia?

A

A type of anaemia that causes unusually large red blood cells

the red blood cells have low levels of haemoglobin

59
Q

What type of anaemias is shown here?

A

Iron deficiency anaemia

small, pale red cells (low MCV and MCH)

variable shape and size with long thin “pencil” cells

60
Q

What feature is visible in anaemia caused by vitamin B12 deficiency?

A

Hypersegmented neutrophils and oval macrocytes

61
Q
A
62
Q
A

Y2 Clinical Pathology (76 decks)

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