Morphogenesis of the palate in the baboon (Papio cynocephalus)

A controlled breeding program was used to collect baboon embryos of known insemination ages. Serial sections of the palatine region of 37 embryos and fetuses from 30 to 64 days (d) (estimated fertilization age) werestudied microscopically and by graphic or wax reconstruction. One 100‐day fetuswas partially dissected. Nasal placodes appeared in Stage XIV (30 d, 4.3–6.0 mm).By Stage XVI (33–36 d, 6.9–9.0 mm) nasal pits developed. The primary palate and palatine processes were present at Stage XVII (36 d, 11.3–11.6 mm). Subsequent development produced rostrodorsal and vertical lengthening of the palatine processes. Rostrally they slanted caudomedially toward the base of the tongue, and dorsally they remained vertically oriented lateral to the tongue in Stage XXI (43–45 d, 18.3–19.6 mm). In Stage XXII (47 d, 22–24 mm) the midpalatine processesbegan to rotate to a horizontal position. By Stage XXIII (45–50 d, 25.8–28.0 mm)the rostral two‐thirds of the palatine processes were horizontally oriented cranialto the tongue. They were fusing to each other and to the nasal septum. The dorsalone‐third of the palatine processes were assuming a horizontal position by medialprojection. In the 53‐d fetuses (39.6–48.0 mm) the hard and soft palates wereformed except for the uvula, which remained divided until sometime after 64 d(63.0 mm). Epithelial remnants were not formed in the soft palate, suggestingthat this area was formed by mesenchymal merging without epithelial fusion.