(A-F) Hematoxylin-eosin staining in the vocal fold transversal sections showing the vocal fold morphology at embryonic stages E10.5 (A), E11.5 (B), E13.5 (C), E15.5 (D), E16.5 (E) and adult (F). Abbreviations: EL, epithelial lamina; ESO, esophagus; LPH, primitive laryngopharynx; SPT, septum; VF, vocal folds.