Constituents of Blood and Haematopoeisis Flashcards
What is blood?
cells suspended in liquid plasma
What are the 3 main types of blood cells?
Red blood cells
White blood cells
Platelets
What are the main functions of the blood?
Fight infection
Transport oxygen
Prevent bleeding
How are blood cells made? What cells do they come from?
haematopoiesis = formation of blood cells
small pool of pluripotent stem cells produce all types of blood cells
Describe the sites of haematopoeisis in an embryo compared to that of an adult?
Embryo = Haematopoiesis in Yolk sac -> liver -> Bone marrow
Adult = not all bones contain bone marrow
Haematopoiesis is restricted to:
- skull, ribs sternum, pelvis, proximal ends of femur
- aka the AXIAL skeleton
What happens to a stem cell in order to make blood
- Proliferation
- Differentiation
- Development of special features of the end cell type
- Stem cells need to be able to self renew
What are the main 2 lineages that a stem cell can follow whilst differentiating into a blood cell?
Myeloid lineage - eventually forms RBCs, platelets, granulocytes and macrophages
OR
Lymphoid lineage - eventually forms T cells, B cells and Natural Killer cells
Describe what happens to the size of most blood cells as they mature?
Get smaller as cells continue to divide
=> cytoplasm always budding off to create other cells
=> primitive cell larger than mature cells
What is erythropoeisis?
Formation of RBCs
How does the red blood cell differ in the blood from in the bone marrow?
In marrow - nucleus still formed and working
Once enters the blood stream, nucleus no longer functions
What is the name given to an immature RBC in the bloodstream?
Reticulocyte
How are platelets formed?
- Nuclei divide but cytoplasm does not
- takes place in megakaryocyte (many nuclei)
- Cytoplasm buds off and forms platelets
What are the main functions of RBCs, WBCs and platelets?
Red cells:
- Carry oxygen
- Buffer CO2
Platelets:
- Stop bleeding
White cells
- Fight infection
- cancer prevention
What are the main types of granulocytes?
Eosinophils (take up eosin stain => red)
Basophils (take up basic stain => purple)
Neutrophils (take up both stains => neutral)
What is the noticeable feature of a neutrophil?
segmented nucleus (polymorph - as no nuclei look exactly the same)
What are the main functions of neutrophils?
- Phagocytose invaders
- Kill with granule contents (die in process)
- Attract other cells to site
What increases the number of neutrophils present in the bloodstream?
body stress:
- infection
- trauma
- infarction
Some drugs can also raise neutrophil count as they make it harder for them to escape the bloodstream
- e.g. steroids
Describe the normal structure of eosinophils
- Usually bi-lobed
- Bright orange/red granules
What are the main functions of eosinophils?
- Fight parasitic infections
- Elevated in hypersensitivity/ atopy
Describe the normal structure of a basophil in the circulation?
- Infrequently found in the circulation
- Large deep purple granules often obscure nucleus
What are the main functions of basophils?
- Circulating version of tissue mast cell
=> Mediates hypersensitivity reactions and bind IgE - Granules also contain histamine
What are monocytes and what is their function?
- Large single nucleus cells
Function
- Circulate for 1 week
- Then enter tissues to become macrophages
- Phagocytose invaders
- Present antigen to lymphocytes
- Attract other cells to site
Describe the structure of a lymphocyte
Mature = small with condensed nucleus and rim of cytoplasm
Activated (atypical) = large with plentiful blue cytoplasm extending round neighbouring red cells
- ALSO nucleus more ‘open’ structure
- This suggests patient is fighting a viral infection
How are the primitive precursors of blood cells identified?
Immunophenotyping
- analysis of proteins (antigens) on surface
Bio-assays
- Culture in vitro and show lineage
HOw can we examine patients in haematology?
- Look at peripheral blood
- Look at bone marrow (+ Specialised tests of marrow)
- Look at other sites of blood production => splenomegaly, hepatomegaly, lymphadenopathy
Where is the most common site for bone marrow aspiration or biopsy?
Posterior iliac crests
What is the difference between a bone marrow aspiration and biopsy?
Aspiration - cells removed are mixed and spread onto a film for analysis
Biopsy - solid sample is taken and sliced like in pathology
What name is given to a bone marrow biopsy?
trephine biopsy
