Comparison of craniofacial tissue interactions during closure of the soft palate in mice and humans. (A) Inferior view of the palatal shelves of an E14.5 mouse embryo showing the gap in the posterior end region. Dotted lines indicate the section planes represented in similarly aged (E14.5) embryos (shown in B,C). (B) H&E-stained coronal section showing outgrowths of the pharyngeal wall in an E14.5 mouse embryo. (C) H&E-stained para-sagittal section showing the posterior tip of the palatal shelves and pharyngeal outgrowth in an E14.5 mouse palate. (D) Inferior view of the palate of an E16.5 mouse embryo showing the opening between the pharyngeal walls. Dotted lines indicate the section planes represented in a similarly aged (E16.5) embryo (shown in E,F). (E) H&E-stained mid-sagittal section showing the interactions between the posterior tip of the palate and epiglottis in an E16.5 mouse palate. (F) H&E-stained para-sagittal section showing the fusion between the posterior tip of the palate and pharyngeal wall in an E16.5 mouse palate. (G) Inferior view of the palatal shelves of a 57-day human conceptus showing the gap at the posterior end region. Dotted line indicates the section plane represented in similarly aged (57 and 58-day) conceptuses (shown in H,I). (H) H&E-stained coronal section showing the unfused palatal shelves in the posterior end region of a 57-day human palate. (I) H&E-stained coronal section showing the mediolateral fusion of the palatal shelf and pharyngeal wall in the posterior end region of a 58-day human palate. (J) Posterior view of the fused palate of a 59-day human conceptus showing the uvula. Dotted line indicates the section plane represented in a similarly aged (58-day) conceptus (shown in K). Arrowheads indicate the palatopharyngeal arch. (K) H&E-stained mid-sagittal section showing that the posterior tip of a 58-day human palate is not in contact with the epiglottis. (L) H&E-stained coronal section showing the MEE at the posterior tip of a 58-day human palate. Arrowhead indicates the less-organized, multi-layered cuboidal epithelial cells. ep, epiglottis; op, oral pharynx; np, nasal pharynx; pw, pharyngeal wall; sp, soft palate; tn, tongue; tr, trachea; uv, uvula. Scale bars in (A) for (A,D,G,J), 1 mm; in (B) for (B,C,E,F,H,I), 500 μm; in (K), 1 mm; in (L), 100 μm.