At S17, the oral cleft extends over the whole width of the face. It is bordered laterally by the developing maxillary processes. Its width remains almost constant between S18 and the end of the embryonic period.
By S15-17, the nasolacrimal groove develops between the lateral nasal process and the maxillary process. At S18, the furrow begins to disappear and the epithelia fuse together at the surface. An epithelial cord remains in the interior, forming the initially solid nasolacrimal duct. The canalization of the lacrimal ducts begins by S23.