<prompt> Buccopharyngeal membrane consist ofMesoderm and endodermEctoderm and mesodermEctoderm, mesoderm and endodermEndoderm and ectoderm  <response>: There is no mesoderm in the prochordal plate, so this region remains relatively thin, and later forms the buccopharyngeal membrane. The buccopharyngeal membrane breaks at 4th week . The mouth is bidermal in development. It is derived paly from the stomatodeum ectodermal and paly from the cranial pa of the foregut endodermal. Hence its epithelial lining is paly ectodermal and paly endodermal and the demarcation between the two is buccopharyngeal membrane. Ref: Inderbir Singhs Human Embryology, eleventh edition, pg. no.,68,69,163. 