The Anatomy of the Nasal Cavity

The nasal cavity consists of all the bones, tissues, blood vessels and nerves that make up the interior portion of the nose. The most important functions of the nasal cavity include warming and humidifying the air as you breathe and acting as a barrier for the immune system to keep harmful microbes from entering the body.

Anatomy

The inside of the nose, including the bones, cartilage and other tissue, blood vessels and nerves, all the way back posteriorly to the nasopharynx, is called the nasal cavity. It is considered part of the upper respiratory tract due to its involvement in both inspiration and exhalation.

The Vestibule

The most anterior portion of the nasal cavity is called the vestibule. The exterior nares, or nostrils lead into this portion of the nasal cavity which is essentially just a short passageway lined with hair that leads into the respiratory region of the nasal cavity.

The Respiratory Region

The respiratory region makes up the largest portion of the nasal cavity. The specialized tissue in this area functions to aid in the respiratory process. This part of the nasal cavity is lined with ciliated pseudo-stratified epithelium and mucus-secreting goblet cells.

Ciliated pseudo-stratified epithelium is a type of tissue that has tiny hairs (cilia) that project out of it and move back and forth to sweep mucus out of the respiratory tract. The goblet cells secrete the mucus.

The Olfactory Region

The apex (uppermost pyramidal area) of the nasal cavity contains all of the receptors and cells necessary for olfaction, or your sense of smell.

The Nasal Septum

The nasal septum is the wall in the middle of the nasal respiratory cavity. It is made up of the septal cartilage, the vomer bone, and the perpendicular plate of the ethmoid bone. The septal cartilage sits on top of the vomer bone and in front of the ethmoid bone, which it joins further back.

Bones

There are 12 bones that contribute to the structure of the nasal cavity. They are the nasal bone, maxilla, sphenoid, vomer, palatine, lacrimal, and ethmoid bones. The first four bones listed are paired (two on each side) The ethmoid bone makes up the largest portion of the nasal cavity.

The Turbinates

Inside the nasal cavity are three curved shelves of bone called turbinates or nasal conchae. They project from the lateral walls of the cavity and are called the superior, middle and inferior turbinates.

The space between the turbinates is called the meatus. The superior turbinate projects from the ethmoid bone and is somewhat separate from the other two turbinates.

Nerves

There are many nerves that are involved in the function of the nasal cavity. Some of the most notable include the olfactory nerve, nasopalatine nerve, trigeminal nerve, and nasociliary nerve.

Blood Vessels

The nasal cavity has a vast and complicated blood supply. Most of the vessels that supply the nasal cavity branch off from the carotid artery and include the anterior ethmoidal artery, posterior ethmoidal artery, sphenopalatine artery, tgreater palatine artery, superior labial artery, and lateral nasal arteries.

These arteries form connections with each other called anastomoses. The blood vessels in the nasal cavity are essential to the function of warming and humidification of the air you breathe.

Blood is carried away from the nasal cavity via a network of veins that drain into the pterygoid plexus, facial vein, or cavernous sinus.

Anatomical differences may be found in the blood vessels that supply and drain the nasal cavities. For example, some individuals may be born with nasal veins that join with the sagittal sinus.

Function

There are three main functions of the nasal cavity which are: olfaction, respiration, and the role this part of the body plays in immunity.

Olfaction

Olfaction is the sense of smell. This occurs in the olfactory region located at the apex of the nasal cavity. This portion of the nasal cavity is lined with specialized cells called olfactory epithelium, which is interspersed with neurons containing sensory cilia.

Synapses from these neurons relay signals to the trigeminal and olfactory nerves so that olfactory information can be relayed to the brain.

The sense of smell is vital in protecting us from harm (dangerous chemicals, fire, etc.). It is necessary for nutrition and closely linked to our sense of taste. It also conveys sensations of pleasure.

Respiration

It is necessary for inhaled air to be warmed and humidified before it reaches the lungs. This is mainly done in the respiratory portion of the nasal cavity which is lined with ciliated pseudostratified epithelium.

The cilia holds on to mucus and the moisture of the mucus plays a role in the humidification of inhaled air. Also, the turbinates work to slow down airflow and keep air contained in the nasal passageways long enough to be warmed and humidified.

Immunity

Cilia on the cells of the tissue lining the nasal cavity combined with mucus (from the goblet cells) have a combined role in filtering the air that we breathe. Small particles and germs are trapped in the nasal cavity by the mucus and the cilia works to sweep the mucus out of the passageways.

Associated Conditions

Rhinitis

Rhinitis is an extremely common condition that most people will experience many times. It is an inflammation of the mucous membranes lining the nasal cavity and adjacent areas that leads to symptoms such as runny nose, congestion, and sneezing. It can be caused by an infection such as the common cold or allergies.

Epistaxis

Epistaxis is just a fancy medical term for a bloody nose. The nasal cavity is highly vascularized and bloody noses are common. They can be caused by trauma to the nose, dry nasal passageways, using medications that thin the blood, or chronic conditions such as hemophilia, very high blood pressure, or chronic rhinosinusitis.

Deviated Septum

While most people are born with a septum that is not exactly centered, some people can be born with a septum that is so far to the left or right that it creates difficulty breathing or other problems. This can also occur as the result of trauma to the nose. Surgery to repair deviated septum is very common.

Enlarged Turbinates

Enlarged turbinates can create symptoms such as congestion as well as preventing the nasal passageways from draining properly which can lead to sinus infections and other symptoms. Turbinates can be surgically reduced.

Tests

When evaluating the nasal cavity and associated conditions your healthcare provider may use several tests. Sometimes the inferior portion of the nasal cavity can be visualized simply using a light. If more visualization is needed an endoscope may be used or medical imaging tests may be helpful such as a computed tomography (CT) scan.

Cultures of mucus secretions can be helpful in diagnosing upper respiratory infections. In the COVID-19 pandemic, testing of nasal cavity swabs for viral antigens and viral DNA became widespread. Influenza viral tests may also be done on nasal cavity swabs.