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Abstract

The development of the hepatic diverticulum was examined in 38 human embryos representing somite stages 1, 5, 8 and 10 through 29, inclusive. Interpretations were based on light microscopic study of serial sections of these embryos.

The liver primordium was first identified in a five-somite embryo as a flat plate of endodermal cells continuous with, but lying ventral to, the endoderm of the foregut at the anterior intestinal portal. It is positioned caudal and ventral to the developing heart. This plate of endoderm subsequently undergoes a progressive folding due to differential growth of adjacent structures. During the folding process there is a close spatial relationship between the cells of the endodermal plate and the caudal and ventral endothelial lining of the atrium and the sinus venosus. The result of this folding is the establishment of a “T-shaped” diverticulum which projects ventrally and cephalically from the gut tract. The hepatic diverticulum is established by the 20 somite-stage embryo. This mode of development of the hepatic diverticulum is compared to the classical interpretation and to the development of other visceral organs.