Figure 917

Dynamics of hemopoiesis in embryonic and fetal life. During embryonic and fetal life, erythrocytes are formed in several organs. Essentially, three major organs involved in hemopoiesis can be sequentially identified: the yolk sac in the early developmental stages of the embryo; the liver during the second trimester of pregnancy; and the bone marrow during the third trimester. The spleen participates to a very limited degree during the second trimester of pregnancy. At birth, most hemopoiesis occurs in the red bone marrow, as in the adult.

months gestation birth

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