Haematopoiesis & Blood Cells

Question 1

what is haematopoiesis?

Answer 1

production of mature blood cells from precursor stem cells

Question 2

what are stem cells?

Answer 2

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

Question 3

what is the primary site of haematoiesis?

Answer 3

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

Question 4

what is the main sites of haematoiesis in children vs adults?

Answer 4

children - long bones of limbs

adults - skull, ribs, sternum, pelvis, proximal ends of femur (axial skeleton)

Question 5

what does the common myeloid precursor differentiate stem cells into?

Answer 5

B cells, T cells, NK cells

Question 6

what does the common myeloid precursor differentiate stem cells into?

Answer 6

megakaryocyte / erytheroid precursor -> RBC and platelets

granulocyte / macrophage precursor -> macrophage, basophils, eosinophils, neutrophils

Question 7

what is the main stimulant for erythropoiesis?

Answer 7

reduced oxygen carrying capacity in blood - stimulates EPO production and release from the kidneys

Question 8

cell lineage - what is polychromatic normoblast?

Answer 8

when Hb begins to be produced

Question 9

cell lineage - what is orthochromatic normoblast?

Answer 9

when nucleus shrinks and all haemoglobin is present

Question 10

cell lineage - what is reticulocyte?

Answer 10

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

Question 11

how does reticulocytes differ from mature RBCs?

Answer 11

reticulocytes are larger and contain RNA (makes them polychromatic)

Question 12

what are the features of a mature RBC?

Answer 12

biconcave shape
no nucleus (no DNA or RNA)
no mitochondria (only glycolysis)

Question 13

what is the lifespan of a mature RBC and how are they removed?

Answer 13

120 days

removed by liver and spleen

Question 14

what is haemoglobin composed of?

Answer 14

4 globin chains and a haem group

haem group: prophyrin ring / Fe2+ (ferrous)

Question 15

there are multiple types of globin chain, with different combinations being seen at different stages of life, what chain is the only constant?

Answer 15

α chain

Question 16

what globin chain is present in foetal haemoglobin (HbF)?

Answer 16

α2 Υ2

Question 17

what are the three different forms of adult haemoglobin?

Answer 17

HbA: α2 β2 (97%)

HbA2: α2 δ2 (2.5%)

HbF: α2 Υ2 (0.5%)

Question 18

what do RBCs rely on for energy?

Answer 18

glycolysis

Question 19

what is the role of the NADH produced in glycolysis of RBC?

Answer 19

required to maintain iron in Fe2+ state (ferrous) - needs to be in this state to bind oxygen

Question 20

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?

Answer 20

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

Question 21

what cell is a precursor to platelets?

Answer 21

megakaryocyte (large cell with large lobulated nucleus)

*platelets are essentially buds of the megakaryocyte cytoplasm

Question 22

what is the lifespan of platelets?

Answer 22

7-10 days

Question 23

what are the key features of neutrophils?

Answer 23

multi segmented nucleus (polymorph)

expresses myeloperoxidase (peroxidase enzyme)

Question 24

what is the name of the process in which neutrophils leave the blood stream?

Answer 24

marginisation

Question 25

what are the functions of neutrophils?

Answer 25

phagocytosis | recruitment of other immune cells

Question 26

what causes neutrophilia (due to reducing marginisation)?

Answer 26

acute inflammation / infection haemorrhage pregnancy drugs = steroids

Question 27

what causes neutropenia?

Answer 27

aplastic anaemia pancytopenia drugs = clozapine, carbimazole

Question 28

what are the key features of eosinophils?

Answer 28

red staining granules | bi lobed horse shoe shaped nucleus

Question 29

what are the functions of eosinophils?

Answer 29

allergy and defence against parasitic infections

Question 30

what conditions are eosinophils raised in?

Answer 30

churg strauss atophy parasitic infections hodgkins

Question 31

what is the most infrequent granulocyte?

Answer 31

basophils

Question 32

what are the key features of basophils?

Answer 32

dark-staining granules that obscure nucleus

Question 33

what is the function of basophils?

Answer 33

thought to be circulating version of mast cells but function not completely known

Question 34

in what conditions is there an increase in basophils?

Answer 34

CML | polycythemia rubra vera

Question 35

what are the key features of monocytes?

Answer 35

produced from same cell lineage as granulocytes | have large cytoplasm and pale, irregular nucleus (kidney shaped)

Question 36

what is the function of monocytes?

Answer 36

they circulate for a couple of days before entering tissues and becoming macrophages where they are involved in phagocytosis and antigen presentation

Question 37

in which conditions are monocytes increased?

Answer 37

``` chronic bacterial infections SLE RA lymphoma leukaemia ```

Question 38

what are the key features of lymphocytes?

Answer 38

small cells with a proportionally large nucleus, with only a small rim of cytoplasm

Question 39

in what conditions are lymphocytes increased in?

Answer 39

infection malignancy hyposplenism

Question 40

in what condition is atypical lymphocytes seen and what do these look like?

Answer 40

glandular fever increase in cytoplasm and wrapping around red cells