The first part of the stomodaeum, lying just within the mouth; its dilator muscles arising on the clypeus, and inserted before the frontal ganglion and its connectives.
The oral cavity, bound by the cheeks of the face, the palate, and the flesh of the mandible, opening onto the mouth and the fauces, and containing the teeth, tongue, gums, and other structures.
The part of the alimentary canal immediately behind the mouth in invertebrates that may be thickened and muscular, eversible and toothed, or adapted as a suctorial organ.
The part of the alimentary canal and respiratory tract that extends from the back of the mouth and nasal cavity to the larynx and esophagus.