Retronasal smell

Retronasal Smell

Diagram of the olfactory system

Retronasal smell, also known as retronasal olfaction, is the perception of odors emanating from the mouth during eating and drinking. This sensory experience is a crucial component of flavor perception, as it combines with taste to create the overall sensation of flavor.

Mechanism

Retronasal olfaction occurs when volatile compounds released from food in the mouth travel through the pharynx to the nasal cavity. This process is distinct from orthonasal olfaction, where odors are detected through the nostrils. The retronasal pathway allows the olfactory receptors in the nasal cavity to detect these compounds, contributing to the perception of flavor.

The process begins when food is chewed, releasing volatile compounds. These compounds travel to the back of the throat and enter the nasal cavity through the nasopharynx. The olfactory receptors, located in the olfactory epithelium, detect these compounds and send signals to the brain, where they are interpreted as specific smells.

Role in Flavor Perception

Retronasal smell plays a significant role in the perception of flavor, which is a combination of taste and smell. While taste is limited to the basic tastes such as sweet, sour, salty, bitter, and umami, retronasal olfaction provides the complex aromas that define the unique flavors of foods and beverages.

The integration of taste and smell occurs in the brain, particularly in the orbitofrontal cortex, where the sensory inputs are combined to create the perception of flavor. This integration is why a blocked nose, which impairs retronasal olfaction, can significantly diminish the ability to perceive flavors.

Differences from Orthonasal Smell

While both retronasal and orthonasal olfaction involve the detection of odors by the olfactory receptors, they differ in their pathways and contexts. Orthonasal olfaction involves the detection of odors that enter through the nostrils, typically from the external environment. In contrast, retronasal olfaction involves odors that originate from the mouth and are perceived during eating and drinking.

The brain processes these two types of olfaction differently, and they can contribute to different aspects of flavor perception. For example, retronasal olfaction is more closely associated with the perception of food flavors, while orthonasal olfaction is often involved in the initial assessment of food before it is consumed.

Clinical Implications

Impairments in retronasal smell can affect the perception of flavor and, consequently, the enjoyment of food. Conditions such as nasal congestion, sinus infections, or neurological disorders can impact retronasal olfaction. Understanding the mechanisms of retronasal smell can aid in diagnosing and treating such conditions.

Related Pages

• Olfactory system
• Taste
• Flavor
• Orthonasal smell