Bone marrow nonneoplastic


Embryonic development

Last author update: 1 December 2006
Last staff update: 11 July 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Embryonic development [title] bone marrow

Nat Pernick, M.D.
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Cite this page: Pernick N. Embryonic development. website. Accessed June 3rd, 2023.
Definition / general
  • In embryo, hematopoiesis (other than lymphoid) occurs in yolk sac with formation of mesenchymal derived primitive erythroblasts
  • Aorta also contributes lymphomyeloid stem cells, as do embryonic liver and bone marrow (Development 2002;129:4147, Ann N Y Acad Sci 2005;1044:41)
  • At weeks 10 to 24, liver is primary hematopoietic organ with production of granulocytes and megakaryocytes in sinusoids
  • At months 4 - 5, bone marrow hematopoiesis begins
  • By birth, liver and spleen have minimal role in myelopoiesis and bone marrow is major site of hematopoiesis
Diagrams / tables

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Blood islands in embryo

Microscopic (histologic) images

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Yolk sac at 18 days

Fetal liver at 17 weeks

Fetal bone marrow at 19 weeks

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