TY - CHAP M1 - Book, Section TI - The Head, Face, and Neck A1 - Reeves, Travis D. A1 - Baldassari, Cristina A1 - Derkay, Craig S. A2 - Kline, Mark W. PY - 2018 T2 - Rudolph's Pediatrics, 23e AB - The critical period of cervicofacial growth and differentiation occurs between weeks 4 through 8 of embryologic development. The beginning of this stage is characterized by the appearance of the frontonasal process—the precursor of the forebrain and upper face—with development soon thereafter of the optic and otic vesicles; the nasal placodes; the primitive mouth, or stomodeum; and 5 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 367-1). 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. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/04/16 UR - accesspediatrics.mhmedical.com/content.aspx?aid=1182906447 ER -