The nasopharynx is the uppermost segment of the throat (pharynx), situated directly behind the nasal cavity and above the soft palate. This box-shaped passageway is a component of the upper respiratory tract. It acts as a junction for inhaled air, linking the nose to the lower parts of the pharynx before air travels toward the lungs.
Anatomical Placement
This superior region of the pharynx is defined by specific bony and soft tissue borders that create its unique structure. The roof of the nasopharynx is formed by the base of the skull, specifically the sphenoid and occipital bones, which provide a rigid superior boundary. Extending from the roof, the posterior wall rests against the upper cervical vertebrae.
The front opens directly into the nasal cavity through two openings known as the choanae, allowing air to pass from the nose into the throat. Inferiorly, the soft palate separates it from the oropharynx (the middle part of the throat), acting as a movable floor.
The lateral walls contain the openings for the Eustachian tubes, which are small passages connecting the nasopharynx to the middle ears. Just behind and above these openings is a ridge of cartilage known as the torus tubarius. High on the roof and posterior wall are the pharyngeal tonsils, commonly referred to as the adenoids, which are a collection of protective lymphoid tissue. The adenoids typically attain their largest size during childhood before naturally shrinking, or atrophying, in adulthood.
Essential Functions
The primary role of the nasopharynx is to serve as a designated channel for air during respiration, ensuring a continuous path from the nose to the lower airway. This segment of the throat is meant exclusively for air and is not involved in the passage of food or liquid. The soft palate elevates during swallowing to seal off the nasopharynx, preventing substances from moving upward into the nasal passages.
A key function is the conditioning of inspired air, a process largely completed in the nasal cavity but delivered via this passage. Air passing through the nasopharynx is brought closer to body temperature and nearly fully saturated with water vapor, achieving conditions similar to those deep within the lungs. The rich blood supply and moist mucosal lining warm and humidify the air before it travels further down the respiratory tract. Furthermore, the lining contains cilia, tiny hair-like structures, that work with mucus to trap and propel debris toward the throat to be swallowed.
The nasopharynx also plays a direct role in maintaining hearing through the function of the Eustachian tubes. These tubes, which open into the lateral walls, allow for the equalization of air pressure between the environment and the middle ear cavity. When a person swallows or yawns, muscles attached to the tubes contract, momentarily opening the passage to balance the pressure. This pressure balancing is necessary for the eardrum to vibrate and transmit sound waves.
Common Health Issues
Due to its role as a respiratory gateway and its location housing lymphoid tissue, the nasopharynx is susceptible to several distinct health concerns. One of the most frequent issues, particularly in children, is adenoid hypertrophy, which is the excessive enlargement of the pharyngeal tonsils. When the adenoids swell, they can obstruct the air passage, leading to chronic mouth breathing, snoring, and obstructive sleep apnea. This enlargement can also press against and block the openings of the Eustachian tubes, causing chronic ear infections and hearing problems due to pressure imbalance.
The most common infection affecting this area is nasopharyngitis, which is medically known as the common cold. This viral infection causes inflammation and swelling of the mucous membranes lining the nasopharynx and nasal cavity. Symptoms like nasal stuffiness, drainage, and a sore throat stem from the body’s immune response to the virus in this sensitive region.
A more serious, though rare, condition is Nasopharyngeal Carcinoma (NPC), a type of cancer arising from the epithelial cells of the nasopharynx. This malignancy is associated with several risk factors, including chronic infection with the Epstein-Barr Virus (EBV). NPC is also more prevalent in specific populations, such as those of Southern Chinese or Southeast Asian ancestry, suggesting a genetic predisposition.
Environmental factors also contribute, including a high consumption of salt-cured fish and preserved foods, especially if consumed during childhood. Other factors include tobacco use and occupational exposure to irritants like wood dust. While it can occur at any age, NPC is often diagnosed in adults between the ages of 30 and 60.