The region where the crescentic masses of the ectoderm and endoderm come into direct contact with each other constitutes a thin membrane, the buccopharyngeal membrane (or oropharyngeal membrane), which forms a septum between the primitive mouth and pharynx.
The area where the crescentic parts of ectoderm and endoderm touch each other creates a thin layer, known as the buccopharyngeal membrane (or oropharyngeal membrane), which separates the primitive mouth from the pharynx.