The nasal airway anatomy plays an important role in respiratory functions. The nose warms the inspired air to body temperature and humidifies the air to 100% relative humidity. Along with smell (olfaction), the nose provides a local immune defense, and it filters the air.
The nose is a natural pathway for breathing and serves as the entrance to the respiratory tract. It is a complex organ, both structurally and functionally. The nose is the organ of smell and provides and conditions air. The nasal cavity is located between the base of the brain and above the oral cavity. It is generally divided into three regions. The vestibule region of the nasal cavity refers to the area surrounding the external opening of the nose. The olfactory region is located at the top of the nasal cavity, and is lined with olfactory cells and nerves that carry smell sensations to the brain. The respiratory region is the largest and functions to humidify, filter, and prepare inhaled air before it travels to the lungs.
Nasal Mucosa and Cilia
The nasal cavity is covered with a mucosal lining containing millions of microscopic hair like structures called cilia. The mucosa traps allergens and bacteria, and those harmful particles are continuously moved towards the back of the nasal cavity by the rhythmic beating of the cilia. This process is an important line of defense, and the production of mucus is controlled by the parasympathetic autonomic innervation. The production of mucus is a natural cycle, but it in some people it can create nasal obstructions and uncomfortable symptoms.
The Nasal Septum and Nasal Valve
The nose is divided into two identical cavities by the nasal septum. The septum is made of cartilage and bone, and ideally, lies in the center of the nose. In about 80% of people, however, the nasal septum is slightly off-center. When the septum is dramatically off-center or crooked, it is know as a deviated septum. A severely deviated septum can prevent proper drainage and airflow and may require surgical treatment. The nasal valve area is formed by the nasal septum, the caudal border, the head of the inferior turbinate and the anterior nasal aperture. This area is responsible for more than two thirds of the resistance produced by the nose, and is typically the narrowest part of the nose. This area can collapse during vigorous breathing, but can also collapses due to structural weakness or trauma during inhalation. Nasal luminal valve obstruction is an abnormality that can cause obstruction and a number of symptoms.
The Turbinates and Meatuses (Sinus Openings)
Lining the nasal sidewalls on each side of the septum are 3 turbinates. These are fingerlike structures made of bone and covered by tissue. The turbinates create elevations in the nose, and between the curved structures are spaces called meatuses. Inhaled air is directed over and under the turbinates and through the meatuses. The mucosa lining of the turbinates, rich in blood vessels, prepares the air by warming/cooling and humidifying it before it travels to the lungs. The inferior turbinate is the bottom most turbinate. It is the largest and serves the most important role in conditioning the air inhaled through the nose. The middle turbinate lies just about the inferior turbinate, and the superior turbinate is the smallest and uppermost turbinate. Enlargement and swelling of the turbinates can impact both airflow and drainage from the sinuses resulting in chronic sinusitis.
Paranasal Sinus Cavities
The sinuses are hollow cavities in the skull. The exact purpose of these air filled chambers is unknown. There are four paranasal sinus cavities located on each side of the nose. The maxillary sinuses are the largest and are located in the cheekbones. The frontal sinuses lie between the eyebrows in the front of the forehead. The ethmoid sinuses are found between the eyes at the nasal bridge, and the sphenoid sinuses lie behind the nasal cavity. The sinus cavities are lined with mucosa tissue. They connect to the nasal cavity through small openings and drain into the meatuses. Inflammation and irritation of the mucosa can prevent the sinus cavities from draining properly. When mucus builds up or bacteria become trapped, acute or chronic sinusitis can result.
Please schedule an appointment with Dr. Trimble if you suffer from nasal airway obstruction.