Development of the face and nasal cavities.

ABSTRACT

The human face develops mainly between the fifth and eighth weeks, following conception. Its development can be traced to five facial primordial appearing around the stomodeum early in the fourth week. There are one frontonasal, two maxillary and two mandibular prominences. By the end of the fourth week, two nasal placodes develop on each side of the lower part of the frontonasal prominences. The early development of the human face is similar to that of other mammals, such as the pig and rat, all of which acquire branchial arches in the early development stage. The rat branchial arches develop at the 4 mm stage and nearly disappear at the 6 mm stage, as the second one grows dorsally and obliterates the cervical sinus. The medial and lateral nasal prominences appear at the 4 mm stage, and at 6 mm the nasal cavities are more extensive than those of a 10 mm pig embryo ; they are at the same stage of development as a 15 mm pig embryo. Currently we use 10 and 15 mm pig embryos as models in studying facial and nasal development. However, in the future, it might be more suitable to use 4 and 6 mm rat embryos because they are easier to obtain.