Haematopoiesis & Blood Cells Flashcards
what is haematopoiesis?
production of mature blood cells from precursor stem cells
what are stem cells?
stable and quiescent cells of mesoderm origin that can self renew indefinitely and undergo differentiation and proliferation to produce a certain type of blood cell
*once a stem cell has started down a specific pathway, it cannot go back
what is the primary site of haematoiesis?
red bone marrow
- when born, all bones have red marrow and are involved
- as we age, amount of red marrow decreased and is replaced with yellow marrow
what is the main sites of haematoiesis in children vs adults?
children - long bones of limbs
adults - skull, ribs, sternum, pelvis, proximal ends of femur (axial skeleton)
what does the common myeloid precursor differentiate stem cells into?
B cells, T cells, NK cells
what does the common myeloid precursor differentiate stem cells into?
megakaryocyte / erytheroid precursor -> RBC and platelets
granulocyte / macrophage precursor -> macrophage, basophils, eosinophils, neutrophils
what is the main stimulant for erythropoiesis?
reduced oxygen carrying capacity in blood - stimulates EPO production and release from the kidneys
cell lineage - what is polychromatic normoblast?
when Hb begins to be produced
cell lineage - what is orthochromatic normoblast?
when nucleus shrinks and all haemoglobin is present
cell lineage - what is reticulocyte?
orthochromatic normoblast becomes reticulocytes when nucleus extruded
these are the final precursors before mature RBCs
reticulocytes pass into the blood stream and circulate before becoming mature RBCs
how does reticulocytes differ from mature RBCs?
reticulocytes are larger and contain RNA (makes them polychromatic)
what are the features of a mature RBC?
biconcave shape no nucleus (no DNA or RNA) no mitochondria (only glycolysis)
what is the lifespan of a mature RBC and how are they removed?
120 days
removed by liver and spleen
what is haemoglobin composed of?
4 globin chains and a haem group
haem group: prophyrin ring / Fe2+ (ferrous)
there are multiple types of globin chain, with different combinations being seen at different stages of life, what chain is the only constant?
α chain
what globin chain is present in foetal haemoglobin (HbF)?
α2 Υ2
what are the three different forms of adult haemoglobin?
HbA: α2 β2 (97%)
HbA2: α2 δ2 (2.5%)
HbF: α2 Υ2 (0.5%)
what do RBCs rely on for energy?
glycolysis
what is the role of the NADH produced in glycolysis of RBC?
required to maintain iron in Fe2+ state (ferrous) - needs to be in this state to bind oxygen
what is the name of the tripeptide structure which helps protect RBCs from reactive oxygen species which causes oxidative damage to cellular enzymes and Hb?
glutathione
- functions as part of enzyme called glutathione reductase
- in order for glutathione to function as part of GR, it needs to be in its reduced form
- this is achieved via the activity of NADPH dependent glutathione reductase
what cell is a precursor to platelets?
megakaryocyte (large cell with large lobulated nucleus)
*platelets are essentially buds of the megakaryocyte cytoplasm
what is the lifespan of platelets?
7-10 days
what are the key features of neutrophils?
multi segmented nucleus (polymorph)
expresses myeloperoxidase (peroxidase enzyme)
what is the name of the process in which neutrophils leave the blood stream?
marginisation
what are the functions of neutrophils?
phagocytosis
recruitment of other immune cells
what causes neutrophilia (due to reducing marginisation)?
acute inflammation / infection
haemorrhage
pregnancy
drugs = steroids
what causes neutropenia?
aplastic anaemia
pancytopenia
drugs = clozapine, carbimazole
what are the key features of eosinophils?
red staining granules
bi lobed horse shoe shaped nucleus
what are the functions of eosinophils?
allergy and defence against parasitic infections
what conditions are eosinophils raised in?
churg strauss
atophy
parasitic infections
hodgkins
what is the most infrequent granulocyte?
basophils
what are the key features of basophils?
dark-staining granules that obscure nucleus
what is the function of basophils?
thought to be circulating version of mast cells but function not completely known
in what conditions is there an increase in basophils?
CML
polycythemia rubra vera
what are the key features of monocytes?
produced from same cell lineage as granulocytes
have large cytoplasm and pale, irregular nucleus (kidney shaped)
what is the function of monocytes?
they circulate for a couple of days before entering tissues and becoming macrophages where they are involved in phagocytosis and antigen presentation
in which conditions are monocytes increased?
chronic bacterial infections SLE RA lymphoma leukaemia
what are the key features of lymphocytes?
small cells with a proportionally large nucleus, with only a small rim of cytoplasm
in what conditions are lymphocytes increased in?
infection
malignancy
hyposplenism
in what condition is atypical lymphocytes seen and what do these look like?
glandular fever
increase in cytoplasm and wrapping around red cells
