coelom
[Gr. koiloma, a cavity]
The fluid-filled cavity in an embryo that forms in the mesoderm as a coalescence of outpouchings of the endoderm. In humans, the coelom develops into the pleural, peritoneal, and pericardial cavities. These fluid-filled cavities are enclosed sacs lined by mesodermal cells that are specialized to transport fluid into and out of the cavity. Organs, e.g., heart, lungs, digestive tract, and liver, protrude into the coelomic cavity, where the surrounding fluid partially isolates them from outside forces. SYN: body cavity.
extraembryonic c.In humans, the cavity in the developing blastocyst that lies between the mesoderm of the chorion and the mesoderm covering the amniotic cavity and yolk sac.