Haemopoeisis

Haemopoeisis

process that maintains lifelong productn of blood cells
main site
1. in fetal life
  1. =liver
2. postnatal life
  1. = bone marrow
origin of all haematopoeitic cells
1. = pluripotent haemopoietic stem cells
  1. crucial for normal bone productn
    1. deficiency-> bone marrow failure
      1. need stem cells to continuously replace dying cells
  2. can be used for Rx
    1. e.g. stem cell transplantation into kids w/ bone marrow failure
in the fetus
1. types of Hb
  1. btw 4 & 8 week's gestation
    1. embryonic Hb
      1. Hb Gower 1
        2 xi chains & 2 episilon chains
      2. Hb Gower 2
        2 alpha chains & 2 episilon chains
      3. Hb Portland
        2 xi chains & 2 gamma chains
  2. > 8 weeks' gestation
    1. HbF (fetal Hb)
      1. main Hb during fetal life
      2. composition
        2 alpha chains & 2 gamma chains
      3. higher affinity than adult Hb
        so holds on to O2 better
        imp cos fetal env hypoxic
in newborn
1. types of Hb present @ birth (all 3)
  1. HbF
    1. =74%
  2. HbA
    1. =25%
  3. HbA2
    1. =1%
2. type of Hb present in 1st year of life
  1. HbF replaced by HbA & HbA2
3. Hb value
  1. at birth
    1. high
      1. cos compensating for low [O2] in fetus
    2. 14-21.5 g/dl
  2. in 1st few weeks
    1. falls
    2. 10g/dl @ 2 months old
    3. pretermies have steeper fall
      1. 6.5 -9g/dl at 4-8 weeks chronological age
4. higher WCC than in older kids
  1. 10-25 x 10^9/L
5. platelets counts @ birth are in normal range
  1. 150-400 x 10^9/L
children 1 year and above
1. Hb types
  1. HbA
    1. =97%
  2. HbA2
    1. =25%
  3. proportion of HbF
    1. very low in healthy kids
    2. if increased is sensitive indicator of haemoglobinopathies
normal av blood vol varies w/ gest age
1. healthy term infants
  1. 80ml/kg
2. preterm infants
  1. 100 ml/kg

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	Created by v.djabatey almost 11 years ago