n. the cavity in an embryo between the two layers of mesoderm. It develops into the body cavity.
(exocoelom) the cavity, lined with mesoderm, that surrounds the embryo from the earliest stages of development. It communicates temporarily with the coelomic cavity within the embryo (peritoneal cavity). Late in pregnancy it becomes almost entirely obliterated by the growth of the *amnion, which fuses with the *chorion.... extraembryonic coelom
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