The Digestive Functions of The Mouth

A comical salivary squirt onto a slice of chocolate cake with the initial discovery of my salivary glands brought up the questioning to what their purpose was and how saliva differs from any other liquid. Along with these questions, the role of the mouth in digestion is its own beast to tackle among the many organs that make up the digestive system with it being the starting point of the gastrointestinal (GI) tract/digestive system and being much more complex than often thought about. Although all the intricacies of how the mouth may help with digestion may not be discovered yet, a broad understanding of the aspects we do know are established in scientific literature. Mechanical digestion, chemical digestion, and the product of these two, bolus, in the mouth are all aspects that are universally well understood and will be broken down to a manageable degree, not going too far into anatomy and biochemistry, in the rest of this article.

Firstly, the mechanical digestion that goes on in the mouth includes mastication (the act of chewing) and the mixing of food with the tongue, incorporating saliva, later to be pushed back to the throat as bolus, a food and saliva mixture. If food is not mechanically digested in the mouth, the following processes of digestion, including the churning of food in the stomach, etc., most likely will become more difficult, because larger food particles may take a longer time to be broken down, which also results in more difficult absorption. Therefore, chewing food thoroughly is extremely important although it is a simple, generally unconscious action. Using the tongue, the mixing of food with saliva, resulting in bolus, is just as crucial as chewing food, because without this thorough mixture called bolus, the enzymes within our saliva will miss out on breaking down the nutrients available. Not only will the larger food particles of food not chewed enough create a greater task for the rest of the digestive system and/or not absorb all nutrients available (1), but food has a much tougher time sliding down the throat when not formed into bolus.

In addition to mechanical digestion, the chemical digestion occurring within the mouth is using saliva to start the processes of breaking down carbohydrates and lipids (fats). This is done by two enzymes in saliva, amylase and lipase, while food is formed into bolus. Amylase, specifically a-amylase or ptyalin, is produced by the parotid and submandibular salivary glands, and it breaks down carbohydrates, starches, into maltose (2). This maltose is later to be broken down into glucose, to be used as energy, by the enzyme maltase in the small intestine. Lipase, more specifically lingual lipase, breaks down dietary triglycerides, the main source of fat stored in the body, starting in the bolus and continuing its process in the stomach (3). Although there is not a bulk of the digestion that happens with carbohydrates and lipids occurring, both enzymes and their digestive processes play a role in digestion significant enough to appreciate them, because of the task that they alleviate for further processes in the digestive system.

In Conclusion, the digestive functions that occur in the mouth include mechanical digestion, chemical digestion, and the production of bolus. Without these mechanisms, the rest of our digestive system would carry the load of their unfinished work, so it is of upmost importance to be aware of how these functions work and how to better practice these actions, especially if you have digestive issues. Some practices, that I will go further into in future content, include chewing slower, consciously, more thoroughly, taking small bites, and working on calm breath work during eating.

(1) N;, Hamada Y;Kashima H;Hayashi. “The Number of Chews and Meal Duration Affect Diet-Induced Thermogenesis and Splanchnic Circulation.” Obesity (Silver Spring, Md.), U.S. National Library of Medicine, May 2014, pubmed.ncbi.nlm.nih.gov/24493207/.

(2) Robyt, John F., and Dexter French. “The Action Pattern of Porcine Pancreatic α-Amylase in Relationship to the Substrate Binding Site of the Enzyme.” Journal of Biological Chemistry, 10 Aug. 1970, www.jbc.org/content/245/15/3917.short.

(3) WA;, Hamosh M;Burns. “Lipolytic Activity of Human Lingual Glands (Ebner).” Laboratory Investigation; a Journal of Technical Methods and Pathology, U.S. National Library of Medicine, Dec. 1977, pubmed.ncbi.nlm.nih.gov/599904/.