Discover How We Swallow

For most of us, swallowing is a function that requires little thought.  We can eat a bag of chips on autopilot while enjoying a movie or sports game of choice.  No attention is paid to the complex, four-stage process that brings a crushed wad of crunchy fried potato slices from your mouth to your stomach.  Nonetheless, even if little attention is paid to this process, it is a biomechanical wonder with your autonomic nervous system firing on all cylinders to facilitate a smooth orchestra of sequential actions at precisely the right time.

The first stage of the swallowing process, the oral preparatory phase, begins before your food even enters your mouth, as your anticipation of deliciousness unconsciously stimulates salivation, or the production of saliva, to assist in breaking down the food on entering your mouth.  Chewing food, with the simultaneous delivery of saliva to said food, makes that food into a softer, more manageable glob.  This glob, referred to as a food bolus, is maintained in the oral cavity by the musculature of the tongue and palate, preventing the premature gravity-dependent launching of this glob into your throat, or pharynx, and unprotected wind pipe. 

The brain receives signals about the size, consistency, and taste of the food glob in your mouth and when ready, signals from the brain are transmitted back to the tongue and throat muscles to initiate the next stage of swallowing—the oral transit phase.  The tongue compresses the food glob posteriorly while the palatal muscles elevate to widen the corridor for the food glob to pass through into the pharynx.  As the glob moves down, additional sensory signals are relayed to different parts of the brain about the food glob and a plan for further coordination of the throat muscles is set into action, with the food entering the pharyngeal (throat) cavity and heralding the third stage of swallowing, the pharyngeal phase.

The pharyngeal phase, also know as the first irreversible step in the process, requires the coordination of 27 muscles. After the food bolus is pushed into the pharyngeal space, it traverses the upper esophageal sphincter enters into the esophagus. The last stage of swallowing is the esophageal phase, which like the pharyngeal phase is it automatic, although much slower.   Once in the esophagus, the bolus is pushed onward by way of peristalsis, the involuntary constriction and relaxation of the esophageal lumenal muscsles. This phase ends once the food glob passes through the lower part of the esophageal sphincter and into the stomach. When swallowing isn’t occurring, the esophageal sphincter remains contracted to prevent reflux from the stomach.

Any abnormality or misfiring in the orchestra of physiologic events that ecncompass swallowing can manifest as dysphagia, or difficulty swallowing.  It goes without saying that dyphagia poses a large burden to those it effects.  Clinicians treating and diagnosing dysphagia may one of several studies to garner a better understanding of what is causing a person to experience dysphagia.  Specifically, a barium swallow study, electromyography,  and/or endoscopy may be utilized individually or in tandem to unearth the underlyhing cause for a person's difficulty swallowing.  That said, the global diagnosis of dysphagia can often be uncovered with a detail oriented patient history.

Oropharyngeal issues typically presents with a history of difficulty initiating swallowing, feeling of food stuck in the pharynx, or coughing and choking during swallowing. When learning about these issues, there may be a need for further evaluation of oropharyngeal dysfunction with a barium video-radiographic study. Esophageal dysfunction, on the other hand, is evaluated on the presence of intermittent or progressive symptoms and by dysphagia to solids, liquids, or both. An endoscopy is generally preformed to assess for most of the esophageal causes of dysphagia.