The nasal cavity consists of all the bones, tissues, blood vessels, and nerves that make up the space inside 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.
This article discusses the anatomy and function of the nasal cavity, as well as health conditions that can affect your nasal cavity.
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Key Facts About the Nasal Cavity
The nasal cavity is lined with a mucous membrane (a lining of tissue) that makes mucus to help keep your nose moist and prevent nose bleeds from a dry nose. There are also little hairs, called cilia, on the inside walls of the nose that filter the air you breathe in to prevent dust and dirt from getting into your lungs.
The nasal cavity is a key component of our sense of taste. Chewing your food releases aromas that travel from your mouth and throat to the nose. Our brains incorporate information from both taste and smell receptors to create the many different flavors we experience.
When foods taste bland or "off," people often blame their sense of taste, when in fact, it may be a loss of the ability to smell.
Anatomy of the Nasal Cavity
The nasal cavity, or inside of the nose, includes the bones, cartilage, tissues, blood vessels, and nerves that extend all the way back to the nasopharynx—the upper part of the throat behind the nose.
The nasal cavity is considered part of the upper respiratory tract because it's involved in both inspiration (breathing in) and exhalation (breathing out).
Vestibule
The most anterior (front) portion of the nasal cavity is called the vestibule. The exterior nares, or nostrils, lead into the nasal vestibule, which is supported by the cartilage of the nose and is lined with tissue that contains short, coarse hairs.
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-stratifiedepithelium and goblet cells.
The 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.
Olfactory Region
The apex (uppermost pyramidal area) of the nasal cavity contains all of the receptors and cells necessary for olfaction—your sense of smell. When odors bind to these receptors, a signal is sent to the brain, leading to the sense of smell.
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.
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. The cells in the nerves communicate with the brain to provide your sense of smell.
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, greater 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 humidifying 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, and 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 thesagittal sinus.
Function of the Nasal Cavity
There are three main functions of the nasal cavity which are: olfaction, respiration, and 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.). The National Health and Nutrition Examination Survey (NHANES) found that 1 in 10 people couldn't identify the smell of smoke and about 15% couldn't identify the smell of natural gas. Sense of smell declines even more as we get older: for people aged 70 and older, 20% couldn't identify the smell of smoke and 31% couldn't recognize natural gas odor.
The sense of smell is also necessary for nutrition and is 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) work together to filter the air we breathe. Small particles and germs are trapped in the nasal cavity by the mucus and the cilia work to sweep the mucus out of the nasal passageways.
Conditions Associated With the Nasal Cavity
There are several health conditions that can affect your nasal cavity, such as inflammation, nose bleeding, congestion, and difficulty breathing.
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 a virus (the common cold), allergies, hormonal changes, or irritants (smoke, chemicals).
Epistaxis
Epistaxis is just a fancy medical term for a bloody nose. The nasal cavity has a vast blood supply 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. Other symptoms may include difficulty breathing through the nose, snoring, difficulty sleeping, nosebleeds, and loss of smell.
Turbinates can be surgically reduced.
Nasal Cavity Tests
When evaluating the nasal cavity and associated conditions your healthcare provider may use several tests. Sometimes the front portion of the nasal cavity can be visualized simply using a light. If more visualization is needed, an endoscope (a thin tube with a tiny camera and a light) 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. During the COVID-19 pandemic, testing of nasal cavity swabs for viral antigens and viral DNA became widespread. Influenza viral tests may also be done using nasal cavity swabs.
When to See Your Healthcare Provider
If you have nasal cavity symptoms such as congestion, runny nose, sneezing, or loss of smell that lasts more than a couple of weeks, talk to your healthcare provider. If you have symptoms such as fever, severe headache, facial or sinus pain, nose bleeds, or breathing problems, see your healthcare provider right away.
Always talk to a healthcare provider about any symptom that is severe or concerning to you.
Summary
The nasal cavity includes all the bones, tissues, blood vessels, and nerves that make up the inside of the nose. It has many functions, including being a key part of your sense of smell, warming and humidifying the air you breathe, and keeping dust and germs out of your lungs. Certain health conditions in the nasal cavity may require treatment. See your healthcare provider if you have nasal symptoms that persist for more than a couple of weeks or become more severe.
