Embryology of the sternum.

Development of the sternum during the growth of the embryo is described. Anterior body wall defects in the thoracic region may be severe, leading to ectopia cordis, or mild, as in skin-covered sternal clefts. The embryologic basis for other sternal abnormalities, such as pectus excavatum and pectus carniatum, is not clear; however, abnormalities of rib morphogenesis and growth are the most likely causes.