The oval-shaped oral cavity located at the apex of the digestive tract and consisting of two parts: the vestibule and the oral cavity proper. Slitlike space in the oral cavity, bounded externally by the lips and cheek, and internally by the gingiva and teeth. Part of the oral cavity bounded laterally and ventrally by the alveolar arches and their contained teeth. Its roof is formed by the palate and it communicates posteriorly with the oropharynx.