The nasopharynx is a specialized part of the human throat, or pharynx, situated at the top of this muscular tube. It serves as a vital passageway for air, connecting the nasal cavity to the rest of the respiratory system. This region plays an important role in preparing inhaled air before it reaches the lungs. Its position within the head allows it to perform several important physiological tasks.
Anatomical Position
The nasopharynx is the uppermost segment of the pharynx, positioned directly behind the nasal cavity and extending downward to the level of the soft palate. Its superior boundary is formed by the base of the skull. This rigid roof and posterior wall contribute to the nasopharynx maintaining an open, vaulted space, ensuring a continuous airway.
The posterior wall of the nasopharynx lies in front of the first two cervical vertebrae. Inferiorly, the nasopharynx is demarcated by the soft palate, a movable muscular flap that separates it from the oropharynx below. Anteriorly, it communicates directly with the nasal cavity through two openings called the choanae.
This section of the pharynx is shaped somewhat like a box, measuring approximately two to three centimeters from front to back and about three to four centimeters from top to bottom and side to side. Its fixed position, supported by the skull base and surrounding muscles, enables its consistent function as an air conduit. The lining of the nasopharynx is primarily composed of respiratory epithelium.
Neighboring Structures
The nasopharynx is connected to several adjacent structures. Anteriorly, it opens directly into the nasal cavity through the choanae. Inferiorly, the nasopharynx transitions into the oropharynx, the middle part of the throat, with the soft palate serving as a boundary. During swallowing, the soft palate moves upward to seal off the nasopharynx, preventing food or liquids from entering the nasal passages.
On each lateral wall of the nasopharynx, there are openings for the Eustachian (auditory) tubes. These narrow tubes connect the nasopharynx to the middle ear cavities, lying roughly 1.25 cm behind and slightly below the inferior nasal concha. A cartilaginous prominence surrounds the opening of each Eustachian tube.
Another structure within the nasopharynx is the adenoids. These are masses of lymphatic tissue located on the roof and posterior wall of the nasopharynx. The adenoids are part of the body’s immune system, acting as a first line of defense against inhaled pathogens.
Key Functions
The nasopharynx performs several roles. Its main function is to serve as an airway, allowing air to pass from the nasal passages into the lower respiratory tract towards the lungs. As air moves through the nasopharynx, it undergoes conditioning. The mucous membranes and cilia lining this region work to warm, humidify, and filter the inhaled air, trapping dust, debris, and microorganisms before they can reach the lungs.
A function of the nasopharynx involves its connection to the middle ears via the Eustachian tubes. These tubes regulate air pressure within the middle ear, ensuring it matches the atmospheric pressure. This pressure equalization is important for the proper vibration of the eardrum and clear hearing.
The adenoids within the nasopharynx contribute to the body’s immune defense, especially during childhood. They help identify and combat airborne germs and pathogens that enter through the nose. This lymphatic tissue acts as a protective barrier, playing a role in the body’s initial immune response.