Answer: endoderm

AnswerCrossword Clue
ENDODERMEmbryonic hypoblast.
endodermthe innermost of the three primary germ layers of an embryo that is the source of the epithelium of the digestive tract and its derivatives and of the lower respiratory tract
endodermthe innermost layer of embryo, also ENTODERM
endodermtissue derived from this layer