Congenital anomalies are the product of errors in embryogenesis (malformations) or the result of intrauterine events that affect embryonic and fetal growth (deformations and disruptions) . The more complex the formation of a structure, the more opportunities for malformation. (See "Genetic and environmental causes of birth defects" and "Principles of teratology" and "Approach to congenital malformations".)
Defects in the formation and growth of the jaw, oral cavity, and pharynx lead to a variety of malformations. The embryology, clinical features, and management of congenital anomalies of the oral cavity and pharynx are reviewed here. Congenital anomalies of the ear, nose, and upper aerodigestive tract are discussed separately. (See appropriate topic reviews).
The oral cavity is separated from the nasal cavity posteriorly by midline fusion of the secondary palate and anteriorly by the approximation of the primary palate to these shelves. The two halves of the lower jaw arise from mesenchyme derived from the first branchial arch (figure 1) and eventually fuse medially. Midline union of the mandibular portions of the first branchial arches, the earliest fusion event in the face, normally occurs during the fourth week of intrauterine life.
The anterior two-thirds of the tongue are formed from two lateral swellings that arise from the first branchial arch. The posterior one-third of the tongue develops behind the foramen cecum from second arch mesenchyme. Thus, the anterior and posterior sections of the tongue have separate innervations and blood supplies.
The parotid glands arise from solid epithelial cords that proliferate from the ectodermal lining of the primitive mouth. The submandibular glands are of endodermal origin .