The nasal region is comprised of the nose, which forms the upper part of the respiratory tract. It is located superior to the hard palate and contains the organ of smell. The nose includes the external nose and the two nasal cavities. It is responsible for olfaction, respiration, filtration of dust, humidification of breathed air, and reception and elimination of secretions from the nasolacrimal ducts and paranasal sinuses.
The external nose is the visible part that projects from the face. It’s pyramidal in shape with its apex anterior in position. The shape of the nose varies from one individual to another in both shape and size. This is due to the differences in cartilages, which make up the majority of the framework.
Anteriorly, the nose is supported on each side by the lateral process of the septal cartilage, the major alar and three or four minor alar cartilages. In addition, a single septal cartilage is present in the midline. It forms the anterior part of the nasal septum, which divides the chamber of the nose into two nasal cavities. The bony portion of the nose is where the nose is continuous with the skull. It’s comprised of the nasal bones and parts of the maxillae and frontal bones. The inferior aspect of the external nose has two oval apertures - the nares. They are bound by the alae of the nose and form the anterior openings of the nasal cavities. The external nose is covered by skin that extends into the vestibules, the area where variable numbers of stiff hairs are present.
The nasal cavities are the uppermost parts of the respiratory tract that contain the olfactory receptors. They have an elongated wedge shape, with a large inferior base and a narrow superior apex. They are supported and held open by a skeletal framework made up of bones and cartilages. The smaller anterior regions of the nasal cavities are enclosed by the external part of the nose, while their larger posterior regions are positioned more centrally within the skull.
As mentioned before, the nares form the anterior openings of the nasal cavities, which open posteriorly into the nasopharynx through the choanae (rigid oval-shaped openings between the nasal cavities and nasopharynx). Mucosa lines the entirety of the nasal cavities except for the area of the nasal vestibules, which are lined by skin. The nasal cavities are separated by several structures: from each other by the nasal septum; from the oral cavity below by the hard palate; and from the cranial cavity above by parts of the frontal, ethmoid, and sphenoid bones.
The arteries that supply the nasal region are the maxillary and facial arteries, which originate from the external carotid; and the ethmoidal branches of the ophthalmic artery, which originates from the internal carotid. The nasal region’s venous supply generally follows that of their corresponding arteries.
The innervation of the nasal region is done by three cranial nerves. The olfactory nerve (CN I) is responsible for olfaction. The trigeminal nerve (V) is responsible for general sensation, where the anterior region is supplied by the ophthalmic nerve (V1), and the posterior region by the maxillary nerve (V2). The greater petrosal nerve of the facial nerve (CN VII) supplies the glands.