In digestion, a food bolus is the mass of food formed in the mouth after thorough chewing and mixing with saliva. This mass is called a food bolus during its journey from the mouth down the esophagus. Once the bolus has passed into the stomach it is called chyme.
When food enters the mouth, it must be prepared for swallowing. Teeth masticate, or chew, the food, beginning the chemical and mechanical process of digestion. Enzymes in saliva break down carbohydrate and starches. Once the lingual nerve of the tongue senses that the food is holding together in a softened ball, it moves the bolus through channels formed by the tongue and palate toward the pharynx at the back of the throat.
Once in the pharynx, the bolus touches receptors that tell the epiglottis to close over the trachea while the food bolus passes so food isn’t aspirated into the airways. At the same time, the soft palate rises up to prevent food from moving into the nose. Because of this, chewing, breathing, and talking cease temporarily.
As the food lump moves from the pharynx into the esophagus, the upper esophageal sphincter opens to allow the bolus to pass, and closes behind it to prevent digestive fluids from entering the mouth. The bolus enters the esophagus, a long, tube-like structure that contracts in rhythmic waves called peristalsis, pushing the bolus toward the stomach. At the end of the esophagus, the lower esophageal sphincter opens, allowing the bolus to enter the stomach and closes behind it to prevent stomach acids and partially digested food from entering the esophagus.
A food bolus obstruction may happen when someone with an underlying condition does not chew food, usually meat, thoroughly, and the food gets stuck in the esophagus. Schatzki rings may cause narrowing in areas of the esophagus, making it difficult for the bolus to pass. Food bolus obstruction can also be caused by peptic stricture, which is a narrowing of the esophagus caused by long-term gastroesophageal reflux disease. Obstructions can be common in the elderly, children, mentally impaired, and those who have suffered a debilitating health problem such as a stroke.
If the obstruction does not resolve on its own, emergency treatment may be necessary. Symptoms of esophageal food bolus obstruction may be pain in the chest, excessive salivation, painful swallowing, or a choking sensation. Endoscopy is frequently the first treatment for an obstruction and can not only remove the obstruction, but diagnose underlying condition that caused it.