An ORAL cavity is a type of cavity located in the mouth, and is commonly referred to as the mouth. It is the space between the lips and the teeth, and is used for speaking, eating, and breathing. A NASAL cavity is a type of cavity located in the nose, and is used for smelling and filtering air. Sinuses are cavities located in the skull, and are connected to the NASAL cavity. They are filled with air and help to reduce the weight of the skull, as well as provide resonance to the voice.