Introduction to Haematology

Question 1

What is blood?

Answer 1

Specialised fluid composed of various cellular components suspended in a liquid called plasma

Question 2

What are the types of blood cells?

Answer 2

3 types:
- Red cells
- White cells
- Platelets

Question 3

Why do we need various types of blood cells?

Answer 3

Various roles
- Transport gases (oxygen + CO2)
- Fight infection
- Prevent bleeding
- Cancer surveillance
- Conduit for hormones, waste products, nutrients from the gut

Question 4

Where are blood cells produced?

Answer 4

In bone marrow

Question 5

What is the process of producing blood cells called?

Answer 5

Haematopoiesis (or hemopoeisis)

Question 6

All different blood cell types are derived from?

Answer 6

A small pool of precursor cells called haematopoeitic stem cells

Question 7

In the embryo, what is the site of haematopoeisis?

Answer 7

Initially in yolk sac
Then the liver, then the marrow with the spleen being a site from 3rd to 7th month

Question 8

What is the site of haematopoiesis at birth?

Answer 8

Mostly marrow, but liver and spleen when needed

Question 9

As we grow into adulthood, what is the site of haematopoesis?

Answer 9

Active marrow sites decrease but retain the ability, active marrow is confined to axial skeleton eventually (ribs, skull, vertebrae, pelvis and proximal long bones)

Question 10

Describe features of haematopoietic stem cells

Answer 10

Few in number - capable of generating wide range of progeny
Huge number of progeny need to be made to maintain status quo
So marrow is metabolically active and energy demanding

Question 11

What has to happen for a stem cell to become a blood cell?

Answer 11

Proliferation
Differentiation into specialist cell
But also, stem cell renewal for the future

Most stem cells are in a quiescent state

Question 12

Describe orderly progression of maturation to mature forms in the marrow

Answer 12

Question 13

Describe the orderly progression of erythropoiesis

Answer 13

Question 14

Describe how thrombopoeisis is different

Answer 14

Question 15

What are the different types of white blood cells seen in blood?

Answer 15

Granulocytes (most common)
Monocytes
Lymphocytes

Question 16

What types of granulocytes are there?

Answer 16

Eosinophils
Basophils
Neutrophils

Question 17

What stain do eosinophils take up?

Answer 17

Granules take up eosion which is red and acidic

Question 18

Basophils take up what dye?

Answer 18

Granules take up basic (alkali) dyes which are densely blue

Question 19

Neutrophil granules take up what dyes?

Answer 19

Are fine and are a neutral mix of blue and red

Question 20

What is the structure of neutrophils?

Answer 20

Segmented nucleus (randomly, up to 4 lobes usually, also called polymorphs because nuclei look unique)
Neutral staining fine granules

Question 21

What is the function of neutrophils?

Answer 21

Phagocytosis
Granule release to break down tissues (elastases), and attract other cells via small molecules released
Short lived cells not capable of further division
Numbers are increased with body stress e.g bacterial infection, trauma, infarction

Question 22

What is the structure of eosinophils?

Answer 22

Usually a bilobed nucleus
Stuffed with bright orange / red granules

Question 23

What is the function of eosinophils?

Answer 23

Numbers are increased with parasitic infections; involved in hypersensitivity (allergic) reactions
So often elevated in patients with allergic conditions e.g. asthma, atopic rhinitis

True function may be less apparent, involved in immune regulation

Question 24

What is the structure of basophils?

Answer 24

Large deep purple cytoplasmic granules often obscuring the nucleus
Granules contain histamine and heparin like molecules

Question 25

What is the function of basophils?

Answer 25

Circulating version of a tissue mast cell
Role remains unclear
Mediates hypersensitivity reactions IgE mediated histamine release

Question 26

What is the structure of monocytes?

Answer 26

Large single nucleus
Scant faintly staining granules, cytoplasm light blue and often vacuole

Question 27

What is the function of monocytes?

Answer 27

Circulate for about a week then enter tissues to become specialised tissue macrophages, so much longer lived than neutrophils

Role in tissue is to phagocytose, engulf and destroy infective organisms, and presenting antigen to immune cells and releasing signals to attract other cells

Question 28

What is the structure of lymphocytes?

Answer 28

Maturę lymphocytes are small with condensed nucleus and limited cytoplasm

Activated (often called atypical) lymphocytes are large with plentiful blue cytoplasm often extending up to neighbouring red cells on a blood film and with a larger less condensed looking nucleus

Question 29

What is the function of lymphocytes?

Answer 29

Numerous types of lymphocytes with differing functions (B, Th1, Th2, Tc, NK, etc.) that are often impossible to distinguish morphologically

The cognate response to infection - the brains of immune system

Question 30

How can we identify primitive precursors?

Answer 30

Question 31

What can immunophenotyping be used for?

Answer 31

Question 32

What tools do we have to look at haematopoeitic system?

Answer 32

Peripheral blood (FBC and blood film)
Bone marrow (marrow biopsy)
Specialised tests (immunophenotyping, genetic tests)
Look at other sites of relevance to blood production (e.g. splenomegaly, lymphadenopathy)

Question 33

What can be used to identify different blood molecules?

Answer 33

Automated FBC analyser

Question 34

Where can we do a bone marrow biopsy from?

Answer 34

Posterior iliac crest
- Insert needle, removed trochar and aspirate marrow

Question 35

What is a bone marrow trephine biopsy?

Answer 35

A core of marrow is removed, decalcified, paraffin embedded and cut to thin sections for staining

Question 36

Draw the haematopoeitic tree

Answer 36