Nose

From ArticleWorld

The nose is a bony and cartilaginous protuberance in the face of mammals that serves multiple functions. Depending on the particular mammal, the function of olfaction, or smelling, can be very acute.

Anatomy

The nose is formed by several bones and surrounding cartilage. The nose is divided into two halves. Each of the two openings is called a nostril. They together form the nares. The air that enters the nostrils is separated by a bony and cartilaginous nasal septum. The nasal septum is partially formed by the perpendicular plate of the ethmoid bone and by a bony projection of the maxillary bone called the vomer. The exterior of the nose is shaped by the nasal bone, cartilage and by fibrofatty tissue.

Each nasal cavity is medially bordered by the nasal septum and laterally by the inferior, middle and superior conchae or horizontal projections into the cavity. The area near the superior concha is the olfactory region and the remainder of the cavity is called the respiratory region. Beneath two of the conchae are openings to sinuses such as the maxillary sinus and the ethmoid sinus. The sphenoidal sinus opens above the superior concha and the nasolacrimal duct opens beneath the inferior concha.

Behind all of the conchae is the opening to the auditory or “Eustachian tube”. This is the tube that can become blocked and “pop” at altitude variations and can result in the formation of ear infections when the tube is blocked with secretions and cannot properly drain the middle ear.

Function

The upper olfactory region of the nose has no hair cells and is covered with a membrane made of supporting cells and olfactory cells, which are responsible for the detection of smell.

The respiratory region of the nose is covered in hair cells that catch particles in the air that would otherwise be unwelcome in the lungs. The air is partially warmed in the nose and inhaled toward the nasopharynx and into the rest of the respiratory system.

Conditions

As the nose receives much of the air one breathes and collects airborne particles, it is prone to respiratory infections, or rhinitis. Such infections can spread into the connecting sinuses, leading to sinusitis. Localized swelling and mucus production can block the Eustachian tubes, leading to secondary ear infections.

Because the nose has a direct connection to the brain via the olfactory system, a bacterial infection of the nasal cavities can spread to the brain leading to meningitis or encephalitis. Viral infections of the nose from rhinoviruses can become secondarily infected with bacteria leading to purulent discharge from the nose and likely to bacterial sinusitis.