Anatomy of the Nose

External Nose

The nose on the outside can be generally divided into three parts. The upper third consists of a set of nasal bones. The remaining lower two thirds are each made up of a paired set of cartilages. The bridge or dorsum of the nose is made up of the nasal bones and middle cartilages. Typically if one has a hump or “bump” on the nose, it is because of this area. One cannot simply shave off this bump without resetting the bones, otherwise the bridge will be flattened, a question that patients often ask Dr. Liu. The lower third consists of a pair of cartilages that span from the side of the nostrils into the middle (see diagram). These form what is called the nasal tip, or the most prominent point of the nose.

Internal Nose

As mentioned, the nose serves several important functions. It is the area of highest airway resistance from the mouth all the way to the lungs when breathing, so any narrowing may cause a great deal of discomfort. This may be especially noticeable in times of increased oxygen demand, such as exercising. The nose warms and moistens the air we breathe, again to make it more comfortable to breathe. The internal nose has several major components – the nasal septum, the turbinates, and the paranasal sinuses.

Nasal Septum

Patients often say, “I have been told I have a deviated nasal septum – what is this?” The nasal septum is the dividing partition between the left and right sides of the nose. It consists of cartilage in the front and bone further back. Lining both sides of the cartilage or bone is mucosa (the pink internal lining of the entire nose and sinuses). A deviated nasal septum simply refers to a septum that is not completely straight. There are varying degrees to the “crookedness”; of the septum. Additionally, the septum itself may be fairly straight but there may be something called a “spur” which is like an overgrowth of cartilage or bone that grows off the septum into the left or right side of the nose. Either a crooked septum or spur may compromise the nasal breathing passageway.

There is an area in the nose called the internal nasal valve – this is actually the area of highest resistance of breathing all the way from the nose and mouth down to the lungs. The septum is one part of this crucial area. The external nasal valve refers to the lower sidewalls of the nose which may collapse during inspiration. If there is a problem with either of these important areas, then sometimes a graft is necessary to improve the breathing.


Each side of the nose has three swellings of tissue called the turbinates (see picture). They extend from the front of the nose to the back of the nose and function to warm and moisten the air when we breathe in through the nose. The inferior turbinate is the largest, and if enlarged, may cause difficulty breathing through the nose. Many factors may cause swelling such as allergies. Most of the sinuses drain into the nose under the middle turbinate, so this is a very important area in regards to proper sinus function.

Not too uncommonly, the middle turbinate is enlarged. It may actually contain an air cell inside of it and act almost like a sinus cell itself and can become infected. An enlarged middle turbinate is called a concha bullosa and can be surgically reduced in size if it causing obstruction of the sinuses on that side of the nose. Also, it may cause unusual areas of contact in the nose leading to facial pain.


Paranasal Sinuses

The sinuses are simply air filled chambers that surround and empty into the nose. There is a tremendous variability to everyone’s sinuses as they develop from infancy to teenage years. There are four sets of sinuses on each side.

  1. Frontal sinuses (located above the eyes in the lower forehead). There is a left and right frontal sinus.
  2. Ethmoid sinuses (extend in between the eyes). There are multiple cells with the anterior and posterior ethmoid sinuses.
  3. Sphenoid sinuses (located in between the eyes but further back). There is a left and right sphenoid sinus and they lie in the center of the base of the skull.
  4. Maxillary sinuses (located behind the cheeks). There is a left and right maxillary sinus.

Interestingly, no one really knows why the sinuses exist. Different theories include lightening the weight of the head, acting as a cushion if there is any facial trauma, and allowing the voice to resonate.

Examination of the sinuses in the office is very difficult even with special fiberoptic cameras. Unless someone has had previous surgery or has certain “natural openings”, the physician cannot directly see into the sinuses. However, since they all drain into the nose, the physician can obtain an indirect view of what may be going on within the sinuses. Sometimes a Cat Scan may be required to obtain the best view of the sinuses. I am often asked “Well isn’t an MRI better?” Actually for the sinuses, a Cat Scan is superior to MRI unless one is looking for a few very specific things (too elaborate for this discussion). This is because a Cat Scan is able to show very fine detail of the bone which is what is most important.

Imagine each sinus is a balloon filled with air. Each balloon then has a tube that connects it with the inside of the nose itself. If everything is working properly, then air is easily passed in and out of the sinus through the tube. Sinusitis simply means inflammation of the sinuses. It may be infectious (viral, bacterial or fungal) or allergic in nature. It may be acute or chronic. Regardless, it occurs when the tube connecting the nose and sinus becomes blocked. Some people are more predisposed towards sinus infections because of the manner in which their sinuses developed. The sinuses need air to constantly circulate in and out to remain clear and healthy.


Normal CT scan of the sinuses

Note the large amount of air (black) inside the sinuses. This is what we want to see.)





Abnormal CT scan of the sinuses

Note the normal air  (blackin the cheek sinuses. Most of the disease (gray) is inside the nose and ethmoid sinuses.





Note the left side is fairly normal with air (black) in the sinuses. There is an enlarged middle turbinate (concha bullosa) on the left side. The right side shows significant disease (gray) in the maxillary sinuses (cheek) and ethmoid sinuses (in between the eyes). 






Nasal polyps are for the most part benign inflammatory polyps. They physically block the breathing passageways and sinuses. As a result, the patient may experience chronic or recurrent sinus infections, nasal obstruction, nasal dripping, headaches, or facial pressure. Simply removing the polyps within the nose typically gives only temporary relief since the polyps tend to grow back. Often to prevent this, a more extensive procedure should be  performed to fully open the sinuses and prevent recurrence. Any associated symptoms with a polyp (especially if only on one side) including severe facial pain, recurrent bleeding, visual problems, or facial numbness sometimes warrant other testing.

Nasal Obstruction

Nasal obstruction can be broken down into 2 major categories:
  1. problems with physical blockage of the nose or
  2. problems with the lining of the nose.

Included in the first category would be such causes as a deviated nasal septum, enlarged turbinates, abnormal sinus development, or a septal perforation (hole in the septum). Nasal obstruction can be a funny thing – it is really how your brain perceives the airflow into the nose. Some people who have wide open nasal breathing passageways, sometimes too open from previous over aggressive surgery, actually complain of problems breathing through the nose.

The lining of the nose serves a very important purpose – to warm and humidify the air we breathe in. The entire inside of the nose and sinuses are actually lined by tiny little hairs called cilia (not visible to the naked eye) that continually sweep mucous into the back of the nose. A proper moist environment is crucial for this system to work properly. Overuse of over the counter nasal sprays such as phenylephrine or oxymetazoline can cause permanent damaging changes to the lining of the nose. The lining is dynamic – that is, it swells up and down throughout the day and in response to certain stimuli. Infection and allergies are common causes of persistent swelling that can cause blockage of breathing.

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