HEMATOPOIETIC-CELL COMPOSITION OF HUMAN FETAL LIVER, SPLEEN AND THYMUS

The haemopoietic cell composition of fetal liver, spleen and thymus wa s studied in human aborted fetuses of 12-22 weeks gestation. Erythroid cells were present primarily in liver and to a lesser extent in splee n. Orthochromatic normoblasts were the predominant erythroid component . Lymphoid cells were seen primarily in the thymus and to a lesser ext ent in the spleen. There were few granulocytic and megakaryocytic cell s in all these organs. A few primitive haemopoietic cells (Haemocytobl asts) were identified only in liver. These observations indicate that during mid-fetal Life (12-22 weeks) the liver contributes primarily to erythropoiesis, the thymus to lymphopoiesis, the spleen to both, and that there is a lack of granulopoiesis and megakaryopoiesis at these s ites.