Endoderm

Endoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer), with the endoderm as the intermost layer. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm.

The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of multiple systems.

Production
The following chart shows the products produced by the endoderm.

Liver and pancreas cells are believed to derive from a common precursor.

The Endoderm has differentiated into distinguishable organs as early as 5 weeks of embryonic development.