The nose and mouth, though seemingly distinct, are internally connected. While they serve different primary functions, they are linked within the human body. This link is fundamental to respiration, digestion, and sensory experiences.
The Anatomical Connection
The pharynx, or throat, directly links the nose and mouth. This muscular tube acts as a shared passageway for both air and food. The pharynx is divided into three main sections: the nasopharynx, located behind the nose; the oropharynx, situated behind the mouth; and the laryngopharynx, which is the lower part leading to both the esophagus and the larynx.
Air enters through the nasal cavity and passes into the nasopharynx, while food and liquids from the oral cavity enter the oropharynx. Both then proceed to the laryngopharynx. An important structure in this pathway is the epiglottis, a leaf-shaped cartilage flap. It is positioned just above the larynx, or voice box, and its primary role is to prevent food and liquids from entering the trachea (windpipe) during swallowing.
Shared Pathways for Essential Functions
The pharynx’s shared pathway enables breathing and swallowing. Air can enter the respiratory system through either the nose or the mouth, both routes ultimately leading to the pharynx and then to the lungs. While nasal breathing is generally preferred for its air-filtering and humidifying benefits, the oral cavity serves as an alternative airway, especially during strenuous activity or nasal congestion.
During swallowing, the epiglottis performs an important action. As food or liquid moves from the mouth into the pharynx, the epiglottis folds down to cover the opening of the larynx, diverting the substance towards the esophagus and away from the airway. This coordinated movement ensures that food travels safely to the stomach, preventing it from entering the lungs. Breathing temporarily ceases during a swallow, highlighting the coordination needed for these functions.
How Connection Influences Senses
The nose and mouth connection influences our perception of flavor, a combination of taste and smell. While the tongue detects five basic tastes—sweet, sour, salty, bitter, and umami—the rich and complex profiles we associate with “flavor” largely depend on our sense of smell. This occurs through a process called retronasal olfaction.
When we chew food, volatile odor molecules are released in the mouth and travel upwards through the pharynx into the nasal cavity, reaching the olfactory receptors. This “smell from within” combines with the basic tastes detected by the tongue, creating the comprehensive flavor experience. Without retronasal olfaction, our ability to distinguish between different foods, such as an apple and a pear, would be significantly diminished.
When the Connection is Compromised
When the nose-mouth connection is compromised, it impacts daily life. A common example is nasal congestion, such as from a cold or allergies. When the nasal passages are blocked, the ability of odor molecules to reach the olfactory receptors via retronasal olfaction is impaired. This leads to a diminished perception of flavor, making food seem bland, even though the basic tastes might still be detected.
A more serious compromise of this connection involves the epiglottis. If the epiglottis fails to close properly during swallowing, food or liquid can enter the trachea, leading to choking. This highlights the epiglottis’s important protective role, preventing substances from entering the respiratory system and potentially causing aspiration pneumonia. Conditions like epiglottitis, where the epiglottis swells due to infection, can severely obstruct the airway, making breathing difficult and requiring urgent medical attention.