The nasal nares are the two external openings of the nose, commonly known as the nostrils. These openings represent the beginning of the respiratory tract, acting as the primary gateway for air to enter the body during inhalation and exit during exhalation. The nares lead directly into the nasal cavity, making them the initial and most exposed point of contact between the outside environment and the internal respiratory system. This function means the nares play a direct role in maintaining the health and preparation of the air we breathe.
The Physical Structure
The term nares refers specifically to the two anterior openings, which are supported by the cartilage and bone structure of the nose. Just inside the external nares is a small, expanded area called the nasal vestibule, which is lined with skin, not the typical moist respiratory tissue. The nasal septum, a wall made of cartilage and bone, runs down the center of the nose, effectively separating the nares into two distinct air passages.
The lining of the nasal vestibule contains coarse hairs known as vibrissae, which are visible and serve a mechanical filtering purpose. Beyond the external nares, air travels through the nasal cavity before passing through the internal nares, also called the choanae. The choanae are the posterior openings that connect the nasal cavity to the nasopharynx, the upper part of the throat.
Essential Roles in Respiration
The nares and the structures immediately inside them perform three air-conditioning functions that protect the lower respiratory system. The first is filtration, where the vibrissae in the vestibule physically trap larger airborne particles, such as dust and pollen. Smaller particulates and pathogens are subsequently caught by the sticky mucus that coats the inner nasal passages.
The second and third functions involve preparing the air for the lung tissues through warming and humidification. As inhaled air flows across the mucosal lining of the nasal cavity, it picks up heat from the underlying blood vessels. This process raises the temperature of the air, protecting the delicate structures in the lungs from cold air damage.
Simultaneously, the air is moistened by evaporating water from the mucosal blanket, reaching high humidity. This humidification is necessary to keep the respiratory tract hydrated and ensure efficient gas exchange when the air reaches the alveoli. The extensive surface area created by the turbinates (conchae) inside the nasal cavity helps slow airflow, maximizing the time available for warming and moistening.
Common Conditions Affecting the Nares
Impairment of the nares or the adjacent nasal cavity can disrupt normal breathing and the protective functions of the upper airway. Nasal obstruction, or blockage, is a common issue that often originates near the nares due to conditions like the common cold, allergies, or chronic sinusitis. This congestion occurs when the mucosal lining inside the nose becomes inflamed and swollen, narrowing the passage and making it difficult to breathe through the nostrils.
Rhinitis and Polyps
Inflammation of the nasal lining, termed rhinitis, can be triggered by allergens like pollen (allergic rhinitis) or by non-allergic factors such as strong odors or smoke. Both forms lead to symptoms like a runny nose, sneezing, and swelling that directly impede airflow. When inflammation is chronic, the continuous swelling can sometimes lead to the development of nasal polyps, which are non-cancerous growths that physically block the air passage.
Structural Issues and Consequences
A structural abnormality that affects nares function is a deviated septum, where the central wall separating the nostrils is shifted to one side. This deviation can restrict airflow in one nostril, leading to congestion or difficulty breathing during physical activity. Another frequent condition is epistaxis, the medical term for a nosebleed, which often originates from the anterior portion of the septum near the nares.
Nosebleeds are commonly triggered by dry air, which causes the mucosal lining to crack, or by direct physical trauma. Any condition that obstructs the nares reduces the efficiency of air conditioning, forcing a person to breathe through the mouth. This bypasses the natural filtration, warming, and humidification systems, increasing the risk of dryness and irritation in the lower respiratory tract.