1) Ectoderm 2) Exoderm 3) Germ layer 1) Ectoderm 2) Exoderm 
• (n.) The outer envelope of a cell; the cell wall. • (n.) The outer layer of the blastoderm; the epiblast; the ectoderm.
(ek´to-blast) the ectoderm.
Ec'to·blast noun [ Ecto- + Greek ... bud, germ.] (Biol.) (a) The outer layer of the blastoderm; the epiblast; the ectoderm. (b) The outer envelope of a cell; the cell wall. Agassiz. 
Type: Term Pronunciation: ek′tō-blast Definitions: 1. As used by some experimental embryologists, the original outer cell layer from which the primary germ layers are formed; in this sense, synonymous with epiblast. 2. A cell wall. Synonyms: ectoderm