How A Nose Functions
Your nose is the guardian of your respiratory tract. Nose functions are more complex that most people imagine. The visible external part of your nose is only the tip of the iceberg. Three quarters of the nasal channel is hidden behind the outer nose that is seen on the face. It extends horizontally back to the center of your head where it then meets, at a 90 degree angle, the top of your throat. It does not travel straight upwards as many people think. Only about 10% of the airflow goes in this direction straight up towards the root of your nose between the eyes. This is where your nerves of smell are located, right between your eyes. 90% of the inspired air flows directly along the floor of your nose. Your sinuses, of which there are 8, surround the nasal channel deep inside your nose. The four largest, those of your two cheeks and tow in your forehead are known to most people. However there are several smaller sinuses, collectively called the Ethmoid sinuses, separated by your septum, between your eyes and just below your brain. The nerve of smell runs along this interface between the Ethmoid sinuses and your brain. Finally there are the two Sphenoid sinuses located at the back of the nose, in the very center of your head. Surprisingly it is still unclear the function of these nose sinuses.
Your septum is the center wall of your nose. The exterior fleshy strip of skin between your nostrils (the Columella) is just in front of the end of your septum. The Septum divides your nose into two channels. These channels should be nearly of equal size, otherwise your breathing can be impaired and you can experience difficulty breathing freely and normally. People can tolerate their center bone or septum if it is close to the mid line,(maybe not exactly in the dead middle); however if the septum is too far to one side, it blocks that nostril and causes many people to have increased resistance to nasal breathing. This is experienced by people as a blocked sensation. Others feels a feeling of congestion, while others notice difficult, hard breathing.
Your septum can become bent or twisted from breaking due to an injury; although it can also simply grow this way over time. Sometimes the injury wasn’t very severe. The nasal bones don’t necessarily have had to be broken to result in breathing problems. In fact very often the injury has been long forgotten. Many times there wouldn’t have been any visible bruising, nor any nasal bleeding at the time of the injury.
As the septum is made of cartilage in the area that has the biggest effect on your breathing, it takes less force to cause it to break or shift that it does to fracture the nasal bones. Very frequently the initial injury doesn’t cause trouble breathing right away but starts a process of continued shifting of the septum that results in slow change over many years, often decades, before its reaches the stage of causing resistance to breathing and a trip to the doctor.
There is a commonly held belief by many doctors that the initial injury, which decades later eventually produces the deviated septum, occurs during child birth. If anyone has seen the degree of distortion of the cranial bones immediately after vaginal birth, it is certainly easy to imagine the same pressure pushing on the infantile nose causing micro fractures of the soft Septal cartilage.
Sometimes you can see the blockage from a deviated septum if you lift the tip of your nose up while looking in a mirror. Much, much more often the narrowing from the deviated septum that causes nasal obstruction is further inside and can be seen only with medical instruments. As the cross sectional area expands as the air travels into the back of the nasal channel, deviations of the deep interior septum have less and less impact on breathing. The critical area where the airflow is most restricted starts about an inch inside the nostrils. It is about an inch long. Doctors have called this area the Nasal Valve.
Nasal Valve and Nose Function
The area about an inch inside your nostrils is the smallest cross sectional area of your entire respiratory tract. It acts as the valve or choke point of your breathing. Two thirds of all the resistance to airflow, from the start of the nostrils to the end sacks of the lungs (alveoli), is found over this short segment of about an inch or so. Your body controls the Nasal Valve by round areas of flesh, called the Turbinates, located on the sidewalls of your nasal channels. They are very, very vascular. The large number of blood vessels inside of your turbinates can quickly expand with blood and cause your turbinates to rapidly swell up. The regulation of the swelling of the turbinates is controlled by your nervous system. The discovery of the nasal valve occurred here in Toronto by Drs. Phil Cole and Jim Haight in 1983. It was a landmark paper that 30 years later is still being cited in our literature.
Nasal Cycle and Nose Function
This is called the nasal cycle and is another example of the many cyclic changes going on inside our bodies. Other body cycles include the sleeping/awake cycle, the secretion of several hormones and the regulation of parts of the autonomic nervous system. This nasal cycle of congestion and decongestion is controlled by nerves arising from your brain. In most people, at any given time, one turbinate is congested and swollen while the other is decongested and shrunk. This causes most of your breathing to be through one side of your nose, while the other side is mostly blocked and resting. After a few hours it switches and the open, decongested nostril becomes the congested and stuffy one. The changeover takes less than a minute to happen. Most people are unaware of this cycle, although it is present in 85% of people. This lack of awareness is because the overall resistance through the two nasal channels of breathing remains the same. There are also similar areas filled with blood vessels on both sides of the septum. These round areas the size of a quarter are called the Septal Swell Bodies and are found adjacent to the inferior turbinate. They function in a similar manner as the turbinates. Sometimes the nervous control of the turbinates is abnormal and results in blocked and uncomfortable breathing. A ‘cold’ in the nose or hay fever are two other very common causes for your turbinates to be temporarily swollen. Lying down has an effect on the turbinates. The dependent side swells and therefore becomes blocked. Surprisingly this effect is caused by pressure around the 5th rib located under your arm, and not from the fact of lying down. If you were to lie down but not allow pressure on this area, the effect doesn’t occur. Likewise if you stand while pressing on this area, that side will congest. This fact has been known to practitioners of Yogi and for thousands of years there has been a Yogi crutch designed to apply pressure under the arm.
Your nose helps prepare the air for your body. Your nose acts as a humidifier of the air you breathe in. Regardless of the outside humidity, by the time air has reached the back of your nose it has become almost completely saturated with water. It’s an amazing feat, if you think about it. Furthermore your nose warms the air to body temperature during this short passage too. It also cleans the air of pollution, dust and dirt. And finally it allows you to smell. The nerves of smell are located at the root of your nose, between your eyes. Only about 10% of the airflow reaches this area. The vast majority of air flows horizontally backwards to where the end of the nose and the top of your throat meet. As it flows along, the air moves across three mounds of flesh inside the nose which warm, humidify and clean the air. These fleshy swellings are the Turbinates, and look and act like the fins of a radiator. The very front of the largest and lowest Turbinate controls the valve of your nose as we have talked about already.
Sense of Smell
Your nose does more than act as a conduit for air to enter the lungs. Although this is of course important, your nose also harbors your sense of smell or olfaction. The 2 nerves of smell are found at the roof of your nose between your eyes. It is the ‘third eye’ of eastern mysticism. Although our visual sense has developed into our primary contact with reality, our olfactory nerves connect into the deep parts of our brain where memories are storied. Hence the return of childhood memories with a smell from the past. Marcel Proust discussed this connection between smell and memory in his monumental book In remembrance of things past. The following is a quote from his famous petite Madeleine scene: “But when from a long-distant past nothing subsists, after the people are dead, after the things are broken and scattered, taste and smell alone, more fragile but more enduring, more immaterial, more persistent, more faithful, remain poised a long time, like souls, remembering, waiting, hoping, amid the ruins of all the rest; and bear unflinchingly, in the tiny and almost impalpable drop of their essence, the vast structure of recollection.”
The Five Functions of the Nose
Besides the nose acting as the entrance of air into your body, it has four other nose functions. Your sense of smell is located inside. In addition your nose warms or cools the air to body temperature by the time it arrives at the top of your throat. Its an amazing thing if you think about it. Whether you are in a 104 degree steam room or skiing in -20 degree weather, the air is at body temperature within a few inches of entering the body. The nose also humidifies the air over this short distance. Finally the air is cleaned of pollution, dust and chemicals as it passes across the lining mucosa of the nose.