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What is Primitive red cells first originates in the early embryonic life is in: and explain in detail?
During embryogenesis, hematopoiesis occurs in extraembryonic yolk sac, the fetal liver, the thymus, and the preterm marrow. The origin of hematopoietic cells is closely tied to gastrulation, the formation of mesoderm cells, and to the emergence of the endothelial lineage. ref ; BD chaurasia ,grays anatomy