The nasal cavity (or cavity of nose, latin: cavum nasi, cavitas nasi) is an irregular, bilateral air-filled space located above the roof of the mouth forming the internal part of the nose. The nasal cavity is an initial part of the respiratory tract and it also lodges the olfactory receptors providing the sense smell.
Most of the nasal cavity is lined with mucosa and it is a part of the upper airway passage. The nasal cavity communicates with all paranasal sinuses, including the ethmoidal air cells and the frontal, sphenoidal and maxillary sinuses.
The bony frame of the nasal cavity is formed by several bones of the skull, it is bounded by the nasal conchae laterally, cribriform plate of the ethmoidal bone superiorly, and the palatal processes of the maxilla and horizontal portion of the palatine bone inferiorly.
The nasal cavity has a vestibule and is bounded by six walls. The nasal vestibule is the most anterior part of the nasal cavity, which is covered by the nasal cartilage and lined with the same epithelium as the skin. The walls of the nasal cavity are formed by several bones of the skull, and the posterior and anterior walls open with large apertures. Anteriorly, the nasal cavity opens with the anterior nasal aperture (also known as the piriform aperture) and continues with the outer part of the nose. Posteriorly, the nasal cavity opens into the nasopharynx through a pair of oval openings called the choanae. The nasal cavity is separated in the middle by the nasal septum, which also forms the medial wall of each half of the cavity.
There are six walls forming the borders of the bony nasal cavity:
The roof of the nasal cavity is formed by the ethmoid and sphenoid bones. The anterior slope of the roof is formed by the cribriform plate of the ethmoid bone, while the posterior slope is formed by the anterior aspect of the body of the sphenoid.
The floor of the nasal cavity is formed by the palatine processes of the maxillae.
The medial wall of the nasal cavity corresponds to the nasal septum, which separates the cavity into two symmetrical parts. The bony nasal septum is formed by the vomer and the perpendicular plate of the ethmoid.
The lateral wall of the nasal cavity is formed by the nasal surface of the maxilla, the perpendicular plate of the palatine bone, the labyrinth of the ethmoid bone, the lacrimal bone, the medial plate of the pterygoid process, and the inferior nasal concha.
The anterior wall of the nasal cavity is formed by the nasal bone and the pair of anterior nasal apertures.
The posterior wall of the nasal cavity is formed by the body of the sphenoid and the paired openings called choanae.
There are several formations in the nasal cavity that are shaped like curved shelves of bone called conchae or conchas. There are three nasal conchae on each lateral wall of the nasal cavity:
The superior nasal conchae and the middle nasal conchae are a part of the labyrinth of the ethmoid bone, while the inferior nasal conchae are separate bones of the skull.
The nasal conchas project into the nasal cavity creating pathways along the lateral wall of the nasal cavity called nasal meatuses. There are five nasal meatuses.
The superior meatus is the passage between the middle and superior nasal conchae.
The middle meatus is the pathway between the middle and inferior nasal conchae.
The inferior meatus lies between the inferior concha and the floor of the nasal cavity.
The common nasal meatus is the space between the conchae and the nasal septum.
And the nasopharyngeal meatus is the space where the superior, middle and inferior meatuses fuse behind the nasal conchae.
The first four of these passages are paired, while the nasopharyngeal meatus is a single pathway behind the conchae.
The nasal cavity is interconnected with other parts of the skull via openings, including:
The openings of the nasal cavity connect each nasal meatus with different cavities or regions of the skull.
The superior nasal meatus is connected with the posterior ethmoidal cells.
The middle meatus presents openings to several paranasal sinuses:
The inferior meatus has an opening for the nasolacrimal canal, which connects the nasal cavity with the orbit.
The common nasal meatus presents the following openings:
The nasopharyngeal meatus features the following openings:
The sphenoidal sinus opens into a small space within the nasal cavity called the sphenoethmoidal recess, which lies superior and posterior to the superior nasal concha.
The arterial blood supply to the nasal cavity is provided by several arteries and their branches, which include:
These arteries ramify to form anastomotic plexuses within the nasal mucosa such as the submucosal cavernous plexus in the posterior part of the septum and in the middle and inferior conchae, as well as numerous arteriovenous anastomoses in the deep layer of the mucosa.
The sensory nerves supplying different parts of the nasal cavity include: