Introduction to haematology Flashcards
What is haematology (2)
Haem = blood
Logos (Greek) =study
What is blood? (3)
It is a specialised fluid, technically a tissue
Composed of a variety of cellular components suspended in a liquid
This Liquid is called plasma and it a variety of molecules including coagulation
factors which you will also be learning about
What are the types of blood cells? (3)
Red cells
White cells (named before stains were available)
Platelets
Why do we need so many types of blood cell? (4)
Transporting gases (oxygen and carbon dioxide)
Fighting infection
Preventing bleeding
cancer surveillance
Where do blood cells come from? (3)
Blood cells are produced in the bone marrow by a process known as
haematopoiesis (or hematopoiesis or hemopoiesis)
All the different blood cell types are derived from a relatively small pool of
precursor cells called haematopoietic stem cells
These stem cells can make all the (very different) circulating blood cells
Sites of haematopoiesis vary with age (6)
In the Embryo= initially in the yolk sac then the liver then the marrow with the spleen being a site from 3rd to 7th month
At Birth= mostly marrow, but liver and spleen when needed
As we grow…= active marrow sites decrease but retain the ability, active marrow is confined to axial
skeleton eventually (skull, ribs, vertebrae, pelvis and proximal long bones)
The haematopoietic stem cell (6)
few in number
capable of generating a wide range of progeny + huge numbers of progeny need to be made to maintain the status quo
the marrow is metabolically very active and energy demanding
Approximately
100 million red cells made per minute
60 million neutrophils made per minute
150 million platelets made per minute
What has to happen to turn a stem cell into a blood cell? (3)
Proliferation
Differentiation into specialist cell
Stem cell renewal for the future despite this actually most stem cells sit in a quiescent state
Thrombopoiesis (platelet formation) (2)
when blast cells divide cytoplasm does not, so increasing number of nuclei accum in a single cell with a very large cytoplasm
The edges of which buds off to form platelets that are released into the bloodstream.
What are the different types of white cells in blood? (3)
Granulocytes (most common)
Monocytes
Lymphocytes
Granulocytes (5)
contain granules that are easily visible
on a stained blood film
named according to the pattern of uptake of stain (eosin and basic dyes)
-eosinophils the granules take up eosin which is red and acidic
-basophils the granules take up basic (alkali) dyes which are densely blue
neutrophils the granules are fine and ‘neutral’ mix of the two colours
Neutrophils - Structure (2)
Segmented nucleus (randomly, up to 4 lobes usually, also called polymorphs because the nuclei look unique)
Neutral staining fine granules
Neutrophils- Function (3)
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’ eg bacterial infection, trauma, infarction
Eosinophils- Structure (2)
Usually a bilobed nucleus
Stuffed with bright orange/red granules
Eosinophils- Function (4)
Numbers are increased with parasitic infections
Involved in hypersensitivity (allergic) reactions
So often elevated in patients with allergic conditions eg asthma, atopic rhinitis
True function may be less apparent - involved in immune regulation
Basophil- Structure (2)
Large deep purple cytoplasmic granules often obscuring the nucleus
Granules contain histamine and heparin like molecules
Basophil- Function (3)
Circulating version of a tissue mast cell
Role remains unclear
Mediates hypersensitivity reactions IgE mediated histamine release
Monocytes- Function (2)
Large single nucleus
Scant faintly staining granules, cytoplasm light blue and often vacuolated
Monocytes- Structure (2)
Monocytes circulate for about a week then enter tissues to become specialised tissue
macrophages, so much longer lived than neutrophils
Role in tissues is to eat things up (macrophage means a big eater) clearing debris,
engulfing and destroying infective organisms, and presenting antigen to immune cells
and releasing signals to attract other cells
Lymphocytes- Structure (2)
Mature 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
Lymphocytes- Function (2)
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 the immune system
How do we identify these more primitive precursors? (2)
Bio-assays
Culture marrow in vitro/in vivo and show a colony of a particular cell type when incubated different growth conditions (so a stem cell
was seeded there, and after a few weeks of growth we see the results).
Immunophenotyping (5)
-Different monoclonal antibodies stick to
different proteins
-Each antibody has a different flurochrome
(coloured tail)
-Detecting what colours are on a cell can
tell you what proteins are on that cell
-Cells of different lineages express different
proteins
-Stem cells express different proteins to
mature cells
Bone marrow biopsy (5)
Perform a bone marrow biopsy from the posterior iliac crest
Insert needle, remove trochar, and aspirate marrow
=Aspirate - low power image of marrow particles and trails
=Aspirate - at high magnification reveals the cellular detail
Bone marrow trephine biopsy, where a core of marrow is removed, decalcified, paraffin embedded and cut to thin sections for staining
