Arey, Leslie B. Department of Cell Biology and Anatomy, Northwestern University Medical School, Chicago, Illinois.
Last reviewed:January 2021
- Hard palate
- Soft palate
- Related Primary Literature
- Additional Reading
The roof of the mouth in those vertebrates whose mouth cavity and nasal passages are wholly or partially separate. A communication between each nasal sac and the mouth cavity first appears in the specialized lungfishes. The two passages open into the front part of the mouth by apertures called the internal nares, or primitive choanae, and the nose then becomes respiratory as well as olfactory in function. A similar adaptation to air breathing when the mouth is closed occurs in amphibians where the premaxillary, median region of the upper jaw serves to separate the nasal cavities from the mouth in front; elsewhere the mouth is an unpartitioned, common chamber. A distinct advance toward a complete palate distinguishes reptiles and birds, with both groups possessing a pair of bony flanges separated by a median cleft so that the incomplete palate provides something of a conduit for the free passage of air. This inverted trough extends from the primitive choanae back to the pharynx. Crocodiles and mammals create wholly separate channels by interposing a complete palate between the air passages and the mouth cavity. The definitive communication of the air channels with the nasal pharynx is known as the secondary choanae. The premaxillary palate of amphibians and the paired unfused palatal shelves of reptiles and birds correspond to progressive stages occurring during the development of the definitive palate in all mammalian embryos.
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