The nose and sinuses form the first part of the respiratory system, the body system that exchanges gases between air and blood. The nose is the main organ that allows air to flow into the lungs. Air enters the body here through two passageways (the nostrils). Each nostril opens up into its own nasal cavity (large spaces inside the front of the face).
The most important function of the nose and nasal cavity is to process each breath before it enters the lungs. This includes:
- Filtering out dangerous particles (e.g., bacteria, viruses, dust, pollen)
- Warming each breath to prevent cold air from damaging sensitive lung tissue
- Adding moisture to each breath to prevent airways and lungs from drying out
In addition, the nose is part of the olfactory system, which senses smell.
The sinuses are air-filled pockets found within the bones of the nose and face. The sinuses appear in pairs on either side of the face. There are four different types of sinuses and, depending on the type, they vary in size from tiny to the size of a walnut. The precise role of the sinuses remains unclear, although they are believed to serve several functions, including:
- Reducing the weight of the skull while preserving bone strength and shape
- Adding resonance to the voice
- Reducing damage sustained during a head trauma by absorbing some of the impact
The nose, nasal cavity and sinuses are the first few components of the respiratory system. The respiratory system is also made up of the pharynx, (the passageway at the back of the throat), larynx (voice box), trachea (windpipe), bronchi (bronchial tubes) and lungs.
About nasal function
The nose is the main organ that allows air to flow into the lungs. For most adults, about 18,000 to 20,000 liters of air pass through the nose every day. The nose offers an entrance to the respiratory system (the body system that exchanges gases between air and blood), through two passageways (the nostrils). The structure supporting the upper part of the external nose is made of bone, while the lower part is made of cartilage.
Each nostril opens up into its own nasal cavity, which is separated by the nasal septum. The septum is made of bone and cartilage and runs from the nostrils to the back of the throat. Bones that project into the nasal cavity (nasal conchae) form a series of folds (turbinates) that increase the surface area of each nasal cavity. The back of the nasal cavity opens up into the airways that lead to the lungs. The nose also acts as the main passageway for air to leave the body when a person exhales. Air can also enter and leave the body through the mouth, or oral cavity.
The most important function of the nose and nasal cavity is to process each breath before it enters the lungs. This filtering process is important for several reasons. Considering the amount of air that passes through the respiratory system each day, it is important that the nose:
- Filter out dangerous particles (e.g., bacteria, viruses, dust, pollen) that could otherwise enter into the lungs, causing damage. Tiny hairs (cilia) and a mucous membrane line the inside of the nose to trap particles before they enter the body. The cilia are capable of small movements and can direct the flow of mucus (a substance secereted by mucous membranes), removing it from the nasal cavity. Sneezing forces air through the nasal cavity and is also effective at removing particles and mucus.
- Warm each breath to prevent cold air from damaging sensitive lung tissue. The large amount of surface area and many blood vessels in the nasal cavity help warm each breath quickly as heat transfers from the blood to the passing air.
- Add moisture to each breath to prevent the airways and lungs from becoming dry and damaged. As air passes through the nasal cavity, moisture is transferred from the mucus secreted by the lining of the nasal cavity into the air.
Because the nose and nasal cavity are so effective at filtering, warming and moisturizing each breath, it is generally better to breathe through the nose than the mouth. Though the mouth can allow a person to inhale more quickly, over time, mouth-breathing can dry out the delicate tissue in the airways and lungs. Furthermore, oxygen may be easier for the lungs to extract from air that has been filtered, warmed and humidified through the nose and nasal cavities.
The nose and nasal cavity are also important for several other reasons:
- The nasal cavity contains smell receptor cells that signal the brain when they encounter different chemicals. The brain can interpret these signals as various smells. The sense of smell also affects a person’s perception of the taste of foods. When people sniff, air flow is increased over the smell receptor cells. This increases a person’s exposure to odors.
- Tears drain into the nasal cavity from the eyes when crying. This drainage occurs through the tear duct known as the nasolacrimal duct. This drainage helps prevent the entrance of foreign particles through the nose and explains why a person’s nose “runs” when crying.
- The eustachian tube runs from the back of the nasal cavity to the ears, equalizing the pressure between them. This connection also allows for ear drainage and ventilation, which helps prevent infection.
- The nasal cavity is connected to several of the sinuses, allowing for drainage from these areas. This allows for the easy removal of foreign bacteria and viruses from the sinuses, which helps prevent infection.
At the back of the nasal cavity is the nasopharynx, which forms the upper part of the throat. The nasopharynx contains adenoid tissue. The adenoid is made up of lymph tissue, which plays a role in fighting infection during the first year of life. After childhood, adenoid tissue shrinks back, reducing the threat of poor sinus drainage and sinus disease. A large adenoid can cause a blockage of the eustachian tubes and may need to be removed by a procedure known as an adenoidectomy.
Common colds and other infections can cause inflammation of the nasopharynx, This can block the eustachian tubes, which results in a feeling of clogged ears.
Patients experiencing prolonged or recurrent nasal problems, such as congestion, sneezing, runny nose or thick nasal discharge, are encouraged to contact their physician. These symptoms may require prompt medical attention because they can aggravate lung problems and lead to other conditions. For example, untreated nasal allergies can increase a person’s risk of developing asthma (a chronic inflammation of the airway tissues), or make existing asthma worse.
About sinus function
The sinuses are hollow spaces located in the face and skull. They appear in pairs on either side of the face. Depending on the type, the sinuses vary in size from tiny to the size of a walnut. The four sets of sinuses are:
- Frontal sinuses. Located in the forehead. There are two of these sinuses, one per side of the forehead. The frontal sinuses vary greatly from person to person in both size and shape.
- Maxillary sinuses. Located in the cheeks between the teeth and the eyes. There are two of these sinuses, one in each cheek. These are the largest of the sinuses, and each can be roughly as large as a walnut.
- Ethmoid sinuses. Located on each side of the nose between the eyes. There are between 6 and 12 of these sinuses on each side of the face. These sinuses are very small.
- Sphenoid sinuses. Located deep behind the eyes, towards the middle of the skull. There are two of these sinuses, one per side. The size, shape and volume of these sinuses vary greatly from person to person.
The function of the sinuses is not entirely understood. Most physicians agree that the sinuses are useful for reducing the weight of the skull while preserving bone strength and shape. The shape of the sinuses and nasal cavity also serve to add resonance to the voice. In addition, sinus cavities may help reduce the damage sustained during a head trauma by absorbing some of the impact.
Like the nasal cavity, the sinuses are lined with mucous membranes – moist layers of tissue that secrete mucus. This mucus helps remove foreign particles that enter the sinuses. The sinuses also have cilia, tiny hairs which push the mucus back into the nasal cavity through small openings (ostia). This drainage is not based on gravity, but rather the efforts of the cilia. From the nasal cavity, the mucus can be removed from the body through either the nose, throat or mouth.
The ostia are very small, and can easily become blocked, preventing the normal drainage of mucus from the sinuses. This often occurs due to the inflammation produced by a cold or allergy (an exaggerated reaction of the immune system to certain foreign invaders that it mistakes as a threat to the body), excessive mucus production or growths such as polyps (bulging growths that develop in the lining of mucous membranes). After the ostia are blocked, inflammation or an infection can occur in the sinuses. This condition is called sinusitis. The air trapped in the sinuses during this condition can cause painful facial pressure, headaches or toothaches.
The ostia openings, mucus production and cilia are all interrelated. If one of the three mechanisms malfunctions, a cycle of problems can develop that often leads to a sinus problem (e.g., infection). This cycle can be difficult to break after it has started. For this reason, people should be aware of any sinus problems or abnormalities that may develop and have any conditions immediately checked out by a physician.
Role in the respiratory system
The nose, nasal cavity and sinuses are the first few components of the respiratory system, which allows the body to exchange gases between air and the blood. The respiratory system is also made up of the following:
- Pharynx. The passageway at the back of the throat. Air travels through the nose and nasal cavity and down the pharynx.
- Larynx (voice box). Air passes from the pharynx through the larynx, located at the upper end of the windpipe.
- Trachea (windpipe). A long tube featuring a series of “C”-shaped rings of cartilage that begins at the larynx and then splits into the bronchial tubes that lead to the lungs.
- Bronchi (bronchial tubes). A pair of tubes that branch off from the trachea, each leading to a lung. Like an upside-down tree, air passageways begin with the trunk (trachea) and divide into large branches (bronchi).
- Lungs. Two spongy, connected organs in the chest that are responsible for the exchange of oxygen and carbon dioxide between air and blood.
Potential problems with nasal & sinus function
In some cases, problems may occur with the nose that can impact a person’s health. For example, allergies (exaggerated reactions of the immune system to certain foreign invaders that it mistakes as a threat to the body), the common cold and other disorders may lead to nasal symptoms such as congestion, sneezing, runny nose, and thick nasal discharge. This can increase the risk of health problems such as asthma (a chronic inflammation of the airway tissues) and bronchitis (an inflammation of the mucous membranes in the bronchial tubes, which connect the windpipe to the lungs) and can lead to several other problems, including:
- Reduced sense of smell
- Dry mouth as a result of excessive mouth breathing
- Bad breath
- Noisy breathing
- Increased ingestion of pollution and germs as a result of mouth breathing
Meanwhile, sinus problems can be related to many problems with the nose, including inflammation, infection and allergic reaction. In many cases, such problems can lead to sinusitis, a condition that occurs when the lining of the sinuses becomes inflamed. Anything that triggers swelling or keeps the cilia (tiny, hairlike projections) from moving mucus (a substance secreted by mucous membranes) can lead to sinusitis. This includes factors such as temperature shifts, changes in air pressure, overuse of decongestant nasal sprays (drugs that reduce nasal congestion by narrowing the blood vessels in the membranes lining the nose), smoking, and swimming or diving. In addition, polyps (bulging growths that develop in the lining of mucous membranes) that grow to block a sinus passage can cause sinusitis. When bacterial or viral infections cause sinusitis, the result is a sinus infection.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians. Patients may wish to ask their doctors the following questions related to nasal and sinus function:
- Am I at risk for sinus/nasal problems? If so, which ones?
- Do my symptoms indicate a sinus/nasal problem or abnormality?
- What risks are associated with my nasal/sinus problem?
- When should I seek a doctor’s attention for a nasal/sinus problem or abnormality?
- What effect do my allergies have on nasal and sinus function?
- Are there steps I can take to promote healthy nasal and sinus function?
- Are my children more likely to develop nasal/sinus problems and abnormalities because I have them?
- Lately, my sense of taste seems to be reduced. Is this likely related to a nasal or sinus problem?
- What treatment options exist for my nasal/sinus problem?
- What are the potential side effects of these treatments?