The nasal cavities are the upper parts of the respiratory tract and are between the orbits. They have walls, floors, and ceilings, which are predominantly composed of bone and cartilage. The anterior openings to the nasal cavities are nares (nostrils), and the posterior openings are choanae (posterior nasal apertures).
Continuous with the nasal cavities are air-filled extensions (paranasal sinuses), which project laterally, superiorly, and posteriorly into surrounding bones.