Topics Discussed: branchial arch; congenital anomaly of head; congenital anomaly of neck; congenital anomaly of the thymus; congenital anomaly of the thyroid gland; dermoid cyst; developmental malformation of branchial arch; ear, nose, and throat; excision of thyroglossal cyst; face; first branchial arch; fourth branchial arch; head; neck; second branchial arch; sistrunk operation for thyroglossal cyst; third branchial arch; thyroglossal cyst.
Sections: Head and Neck Trauma, References.
Excerpt:"The critical period of cervicofacial growth and differentiation
occurs between weeks 4 through 8 of embryologic development.1 The
beginning of this stage is characterized by the appearance of the
frontonasal processthe precursor of the forebrain and
upper facewith development soon thereafter of the optic
and otic vesicles; the nasal placodes; the primitive mouth, or stomodeum;
and five ridges on the ventrolateral surface of the embryonic head,
which is known as the branchial system. Many of
the symmetrically paired skeletal and neuromuscular structures of
the head and neck arise from the first (mandibular), second (hyoid),
third (pharyngeal), and fourth (laryngeal) arches of this fetal
branchial system (Table 372-1). The skull,
facial, and neck bones have begun to ossify by the end of the eighth
fetal week, which coincides with a recognizable human embryonic
face with easily discernible ears, eyelids, cheeks, nose, and upper
and lower lips.Lesions of the anterolateral neck are often of branchial system
origin. Each of the four mesodermal branchial arches were separated
from one another by an external cleft of ectodermal origin and by
an internal pouch of endodermal origin with a thin epithelial plate
separating cleft and pouch. Branchial cleft anomalies are classified
by the likely arch of origin, with second branchial anomalies being most
common.4 They form either sinuses, fistulas, or
cysts. A sinus tract with either an external or internal opening..."
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