The face is formed between the 4th and 8ht week of the development from the facial swellings which appear around the stomodeum (primitive mouth). The facial swellings, formed mainly by the first pair of the pharyngeal arches, constitute the boundaries of the stomodeum: the frontal swelling cranially and the paired maxillary and mandibulary swelling laterally. Two thickenings of the surface ectoderm on each side of the frontal prominence form the nasal placodes. The lateral and medial nasal swellings develop at the margins of the nasal placodes, which then lie in depression called nasal pit.
During the 6th and 7th week, the medial nasal swellings merge with each other to form an intermaxillary segment. This segment gives rise to the philtrum of the upper lip, the upper jaw component (premaxillary part of the maxilla), and the primary palate.