Normal swallowing involves a complex sequence of movements requiring precise muscle control. These movements occur rapidly, with food or liquid only taking two or three seconds to pass from the back of the mouth to the stomach.
Swallowing becomes a problem when an impairment reduces a patient's ability to get adequate nutrition by mouth, or when it raises the danger of aspiration of foodstuffs into the lungs rather than the stomach. Aspiration in turn can lead to potentially life-threatening illness.
There are three stages in the swallowing sequence.
Stage One: The first part of the swallowing sequence takes place in teh mouth. The tongue moves the food or liquid into a cohesive mass and then, with a pushing action, places it at the back of the mouth, where the swallowing reflex is triggered. While the tongue is working, the lips form a tight seal to prevent food or liquid from spilling out.
A swallowing disorder occurs when there is decreased sensation, muscle strength, or voluntary control of the tongue, lips, or other oral structures. Reduced oral strength, control, or sensation can cause food or liquid to fall into the throat before the swallow reflex is triggered and cause aspiration into the open airway to the lungs. These weaknesses also can lessen a patient's ability to begin the swallowing sequence, and therefore limit the amount of nourishment taken by mouth.
Stage Two: The second stage of the swallowing sequence occurs when the swallowing reflex is triggered and the food or liquid moves into the throat. Once the reflex is triggered, breathing momentarily stops and the airway is closed to prevent food or liquid from passing into the lungs.
In this stage, a swallowing disorder could cause the swallowing reflex to be delayed, incomplete, or absent. Food or liquid then can become trapped in the throat, in small pockets called "sinuses" which can hold about one half teaspoon of food or liquid. If more than a small amount is trapped in the throat it can spill into the airway adn result in aspiration when breathing resumes.
It is for this reason that it is important for a patient with a swallowing disorder to take only small bites and swallow completely before taking another bite.
Stage Three: The third and final stage of the swallowing sequence occurs when food or liquid passes from the throat into the esophagus. The esophagus is the tube through which food and liquid reach the stomach. Pockets or strictures in the esophagus also can cause swallowing problems, and must be treated medically or surgically.
Symptoms of a Swallowing Disorder