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why do we have a gag reflex

The gag reflex, also known as the pharyngeal reflex or laryngeal spasm, is a contraction of the back of the throat triggered by an object touching the roof of your mouth, the back of your tongue, the area around your tonsils, or the back of your throat. The reflex helps prevent choking, as well as helping to moderate the transition from liquid to solid foods during infancy. By thrusting objects in the throat toward the opening of the mouth, the gag reflex expels substances that the brain has deemed harmful. In the first few months of a baby s life, this reflex is triggered by any food that a region of the brain stem called the nucleus tractus solitaries (which is wired to nerve endings in the mouth) judges to be too chunky for a baby s stomach to digest. Starting around the 6- or 7-month mark in babies, the gag reflex diminishes, allowing a baby to swallow chunky or solid foods. In children and adults, the reflex is usually only triggered by the presence of an unusually large object in the back of the throat.


However, 10-15 percent of people have a hypersensitive gag reflex (HGR), which continues to get activated by substances in the mouth. Most often, sufferers of HGR
that tend to get stuck in the mouth, such as bananas and mashed potatoes; in extreme cases, oversensitive gagging can cause picky eating or even malnourishment. The reasons why some adults gag while eating are not yet fully understood, but research shows that HGR usually happens in people who did not have solid foods introduced into their diets until after the age of 7 months. Experts recommend starting this process sooner, between the fifth and sixth month of an infant s life, in order to let the baby s gag reflex develop properly. Follow Life s Little Mysteries on Twitter @. We re also on. Closely related to the gag reflex, in which food or other foreign substances are forced back out of the, swallowing generally pushes food through the digestive system into the stomach.


This reflex in particular functions as a protective system for the upper respiratory tract as it not only forces the glottis to close, thereby preventing any substances getting into the airways, but also clears the pharynx of any residual substances by a swallow. This particular reflex is simply one of several aero digestive reflexes, including also the pharyngoglottal closure reflex (in which no swallowing occurs yet the still closes) and the pharyngo-upper esophageal sphincter contractile reflex, which occurs mainly during gastroesophageal reflux episodes. All either forcibly close the glottis or allow the pharynx to remove particles into the digestive tract that may have been forced back up by both this tract and the upper respiratory tract. These reflexes can also protect the airways from any food or liquids that may spill over from the hypopharynx. The hypopharynx is the bottom part of pharynx, and can be considered the first area where the digestive tract splits from the airways.


However, if the maximum capacity of fluids that the hypopharynx can safely hold is exceeded, then this excess fluid spills into the and from there into the lungs. Therefore, these reflexes prevent levels reaching this maximum volume. Since both the digestive system and the respiratory system are connected by the pharynx, there are many problems and diseases that occur when the body is unable to regulate passage of food and air into the appropriate tracts. Perhaps the most preventable cause of damage to these reflexes originates from smoking. One study has shown that, when compared to non-smokers, the threshold volumes (in other words the lowest volume at which one of these reflexes is triggered) for both the pharyngo-upper esophageal sphincter contractile reflex and reflexive pharyngeal swallowing is increased.

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