Palate, the bony and muscular partition which separates the mouth in vertebrate animals from the anterior and posterior nasal cavities. The bony or hard palate forms the roof of the mouth, and consists of the horizontal portion of the superior maxillary bones in front and of the palate bones behind; these form a parabolic arch, bounded in front and on the sides by the upper teeth and their sockets, covered by mucous membrane, and giving attachment posteriorly to the velum palati or soft palate. The width, contractions, elevations, extent, and perforation by larger or smaller incisive or other openings, are valuable characters in estimating the rank of the various subdivisions of vertebrates, those being the highest in which this part is broadest, uniform, and least pierced by foramina, making a complete partition as in man; the changes in the palate bones are connected with corresponding modifications in the sphenoid, and consequently with the whole anatomy of the skull. The soft palate is a movable muscular partition, covered by mucous membrane; its free edge floats above the base of the tongue, having in its centre a conical appendage, the uvula, and on its sides the so-called "palatine arches," of which there are two on each side, the anterior and the posterior; they consist of crescentic folds of mucous membrane enclosing muscular fibres.
The triangular space between the two arches on each side is occupied by the tonsils. The irregularly circular orifice embraced by the palatine arches, which leads from the back part of the mouth into the pharynx, is the " isthmus of the fauces." The mucous membrane of the palate is studded with mucous follicles; its arteries are derived from the external carotid, and its nerves from the trifacial, the glossopharyngeal, and Meckel's ganglion. The muscles of the palatal regions are the circumflexus palati, from the internal surface of the pterygoid process to the velum, stretching horizontally the soft palate, and dilating the Eustachian orifice; the levator palati, from the petrous portion of the temporal bone, raising the palate and carrying it backward; the azygos umdee, vertical, forms the chief part of this organ, raising it with the palate; tho palato-pharyngeus forms the posterior pillar of the palate, depressing the velum and elevating the pharynx; the constrictor isthmi fau-cittm, in the anterior pillars, extending from the base of the tongue to the velum, depress-the latter and elevates the former.
The soft palate is endowed with acute sensibility, and in the neighborhood of the uvula and its arches, and to a less degree on its anterior portion, ministers to the specific sense of taste. The mucous membrane of the palate is subject to inflammations, and the bones are attacked in syphilis and other cachectic diseases; these parts are also liable to arrests of development, in which the mouth and nasal cavities communicate through a fissure, with or without harelip. In this deformity deglutition is difficult, sucking impossible, and the voice indistinct and nasal; surgery is necessary for its relief, and by the operation of staphyloraphy, which consists in placing and keeping in apposition the incised edges of the fissure, a partial or complete closure may be effected; where this is impracticable, relief may be obtained from gutta percha or metallic plates.
The mouth widely open, showing the tongue below, and the hard and soft palate and uvula above, with the isthmus of the fauces in the centre. On the left are shown the fibres of the glosso-pharym.'val and palatine nerves, distributed to the mucous membrane.