General Medical Information

Nasal Embryology

Sharen J. Knudsen
Byron J. Bailey

During the third week of fetal life, a massive frontonasal process develops. The first branchial arch, which divides into the maxillary and mandibular processes, is inferior to the frontonasal process. Ectoderm on the lateral surface of the frontonasal process invaginates to form the nasal pit. The olfactory placode develops around the pit as a horseshoe-shaped tissue mass with a lateral and medial process.

Synchronous events during the fifth through eighth weeks of fetal life produce the definitive structures of the midface. The frontonasal process descends to become the bridge and apex of the nose. The olfactory placodes migrate to the midline and fuse to become the nose. The maxillary processes fuse to form the upper jaw. Midfacial development is a complex event with convergence of the developing sensory organs and respiratory and digestive systems. Congenital defects can occur in regions where all three germ layers interact during developmental activity. In contrast, the mandible develops earlier from a single arch, and fewer congenital anomalies occur in the mandible than in the midface-maxillary region. The medial nasal processes contribute the columella, philtrum, and upper lip. The lateral process fuses with the medial nasal process to form the maxillary arch. The nasofrontal process descends and compresses laterally to form the nasal septum. The medial nasal process contributes to the premaxilla.

In the seventh week of fetal life, chondrification begins in the dense mesenchyma at the caudal end of the notochord. The ethmoid, sphenoid, occipital, temporal, and skull base elements form the chondrocranium. The osteocranium is largely made up of membranous bone, including the vomer, nasal, lacrimal, palate, maxilla, premaxilla, frontal, and parietal bones.