Swallowing takes place in four stages. Different problems can occur at each stage to disrupt the normal swallowing process.
Biting and chewing food takes place in the mouth. At this stage, lack of strength, control or feeling in the mouth -- which may be due to stroke or muscle or nerve disease -- may cause food or liquid to fall directly into the throat and cause choking.
The tongue pushes the food to the back of the mouth where a structure folds over the top of the windpipe to keep food out. At the back of the mouth, the presence of food triggers muscle contractions. At this stage, the muscle at the back of the mouth that opens to allow food into the esophagus may malfunction and cause aspiration (food passing into the windpipe), which results in choking.
Muscle contractions push food down the esophagus. At this stage, lack of or inadequate muscle contractions may cause food to stick in the chest.
Food moves through the esophagus, and the lower esophageal sphincter muscle opens to let food pass into the stomach. At this stage, weakening of this sphincter muscle at the stomach opening may allow acidic stomach secretions to come back up into the esophagus from the stomach, a condition called reflux.
More than 15 million Americans have a swallowing disorder. They can occur at any age. Swallowing problems may be temporary, or they may be an indication of a serious medical problem. There are many causes, including nerve and muscle problems, head and neck injuries and cancer. Or they may occur because of a stroke. Certain medications can also contribute to the disorder.