To understand the physiology of the nose, its functions must be understood. The nose is the only means of bringing warm, moisturized air into the lungs.
It is the main organ for filtering particles in the inspired air. It also provides a first-line immune defense by bringing the inspired air into contact with the mucosa-coated membranes containing immunoglobulin A (IgA).
The inspired air is brought up into the nasal cavity to contact the olfactory nerves, thus providing the sense of smell, which is intimately associated with the sensation of taste.
Dysfunction of any of these systems can lead to symptoms of nasal dysfunction (e.g., congestion, postnasal drainage, facial pressure, headaches, sinus infections).
Awareness of the interrelationship between the upper and lower airways has increased; this concept is now known as the unified airway. The respiratory tract is considered an integrated system, and any process that affects one also affects the other. Therefore, changes in the physiology of the nose and sinuses can affect the lower airways and vice versa.
One of the essential parts of a proper breathing process is the nostrils.
What are the nostrils?
The external openings in the human nose lead to the nasal cavity. They are the connection between the air in the environment and the respiratory tract.
Anatomy of the nostrils
The septum or septal septum forms the wall between the two external nostrils, with the separation visible from the outside. The greater alar cartilage forms the lateral and medial limits of the nostrils, being responsible, together with the lesser alar cartilage, for their general shape.
The two nostrils are generally the same shape and size. However, in some people, the septum can be a bit irregular, making the nostrils of different sizes. In a severe form, such an irregularity is known as a deviated septum.
The primary purpose of the nasal passages is to allow air to enter the nasal cavities so that they can be purified and sent to the following parts of the respiratory tract. It also enables different scents to enter the nose and reach the olfactory region of the nose.
Why do we have two nostrils?
The way humans have two eyes to help perceive the depth of images and two ears to determine the location and distance of the origin of sounds, the two nasal cavities also serve a crucial purpose: to help the nose remain clean.
Due to the purification of the inhaled air within the nasal cavities, all the impurities remain trapped in the nasal mucus, making it more swollen on one side. Therefore, it has less space for air passage. As it removes dust and impurities, the second nasal cavity is responsible for purifying the air and transporting it through the respiratory tract.
When the first one clears, the mucus layer in the other nasal cavity swells and needs time to clean. So, the first side again begins to clean the air actively, and the nasal cycle continues. This is most evident when you have a cold and your left and right noses take turns staying clogged, mainly when you lie down.
Having two nostrils enhances the sense of smell in the same way, as one of the cavities always works better than the other at picking up the odor.
Air flows up into the nostrils, determined by its position and the anterior nasal valve. The air stream then rotates back about 90 ° and flows into the nasopharynx. The air stream turns 90 ° through the pharynx and larynx and flows down the windpipe into the lungs.
The anterior nasal valve is located 1.5-2 cm posterior to the anterior nostrils and is the narrowest portion of the upper airway. The little bit of the upper airway allows close contact between the air stream and the mucosal surfaces. Humidification occurs by evaporation of moisture from the mucosal blanket.
The air is humidified to 75-80%. The heating of the inspired air to 36 ° C results from contact between the air and the abundant blood supply of the nasal membranes, especially the mucosa of the inferior turbinate.
Adults condition more than 14,000 liters of air per day, requiring more than 680 grams of water, about 20% of our daily water intake.