The Gifts of Chewing and Swallowing
Eating and drinking are complex processes that many of us take for granted. This blog post explores the intricate coordination and sensory input involved in chewing and swallowing, highlighting the challenges faced by those with feeding disorders. Discover the fascinating workings of our bodies and gain a deeper appreciation for these everyday actions.
Stay tuned until the end to download a mindfulness chewing exercise designed to heighten your awareness and gratitude for the ability to eat and drink.
Have you ever thought about what it took for you to sip your morning coffee or eat the meal you enjoyed last night? The act of drinking and eating is not only a means to nourish our bodies but a means to bask in the sensory pleasures we experience and connect with those we love.
However, the harsh reality is that millions of people, from infancy to old age, have difficulty eating and drinking or cannot at all. Some require a specialized diet in which they can only eat blended meals while others who cannot consume anything by mouth have a tube inserted through a stoma (hole) in the body where food is delivered directly to the stomach or small intestines.
Below are some statistics on the prevalence of feeding disorders in the pediatric population:
25-45% of typically developing children develop feeding disorders (1).
80% of children with health conditions and/or developmental disabilities have feeding disorders (2).
The Feeding Tube Awareness Foundation report that approximately 20% of children under the age of 18 are tube fed, and there are more than 350 health conditions that can require children to need nutritional support through tube feeding due to an inability to eat by mouth (3).
The ability to chew and swallow are truly gifts that many people take for granted, so in today’s blog post, I would like to take a moment to shed light on the beautiful workings of our body as we dive into the intricate processes of eating and drinking. At the end of the post, I’ve included a mindfulness chewing exercise in hopes to heighten your awareness and appreciation of an act many people have difficulty doing or cannot do at all.
HOW WE CHEW AND SWALLOW
Chewing and swallowing are completed by the synchrony of thousands of sensory receptors and dozens of muscle contractions throughout the head and neck that are controlled by the Central Nervous System (CNS). Communication with the CNS aids in the manipulation of the food we consume using highly precise timing and coordination of chewing and/or sucking, swallowing, and breathing.
Of these sensory receptors are 12 cranial nerves that receive sensory information based on the sight, smell, taste, texture, size, sound, and temperature of food. Along with our hands, the mouth has the highest number of sensory receptors in comparison to the rest of the body. If you google a “homunculus” you’ll find a weird looking figure of a tiny man with disfigured body parts. The size of each body part represents how much of the human brain is dedicated to processing motor and sensory functions for that specific body part. As you’ll see, the hands and mouth are the largest and thus require the most brain power to work efficiently and effectively.
With sensory input comes the motor output of over 50 muscles that coordinate movements of the soft tissue within and around the mouth that form food into what is called a “bolus.” From crunchy crackers to tough meats, highly sophisticated muscle movements of the tongue, jaw, cheeks, and lips are required to form food into a cohesive bolus that is safe to swallow.
The process goes a little something like this:
Depending on the type of food, we either use the central incisors (front teeth) or molars (back teeth) to chew off a piece of food or place bite sized pieces of food in the mouth.
The front and middle portions of the tongue bring food to the molars and remain in constant contact with the food while the back of the tongue remains elevated to prevent anything from escaping and entering the airway.
Along with muscle contractions and support of the inner cheek, food is kept in place for it to be mechanically broken down. As the lip muscles remain contracted to keep the mouth closed and prevent food from escaping, the jaw engages in an up-down motion, which aids the teeth in mashing foods to finer consistencies.
While chewing, the tongue brings food from one side of the mouth to the other within milliseconds with support of the jaw, creating a rocking side-to-side motion known as a “rotary chew.”
Throughout this process, saliva mixes with food and initiates a chemical breakdown through two enzymes called amylase and lingual lipase.
Once a bolus has been formed that is deemed safe to swallow, the tip of the tongue elevates to make contact with the roof of your mouth and pushes the bolus to the back of the throat using a wavelike motion known as peristalsis.
This manner of chewing represents the most sophisticated level of chewing and is not fully developed till around the age of 5 in typically developing children.
Figure 1
In continuation with the process of chewing comes the highly intricate act of swallowing, which (fun fact) occurs 600-800x a day! Once food is pushed to the back of the throat, a reflex is triggered that signals to the brain the initiation of a series of opening and closing of different valves that allow or prevent access to one of two tubes; the trachea (also known as the “windpipe”) and esophagus. As shown in figure 1., the trachea, which sits in front of the esophagus, connects the oral and nasal cavities to our lungs and the esophagus connects our mouth to our stomach. At rest, the trachea remains open to allow air to enter and exit the lungs while the esophagus remains closed. When we swallow, breathing is temporarily ceased as the valve to the trachea closes and the esophagus opens. Food can now safely pass through to the stomach for further digestion.
For a visual of typical chewing and swallowing, I’ve included a youtube link here -> Mastication Chewing Animation
As one can imagine, the mouth and throat are extremely vulnerable areas. One wrong move can become a matter of life or death. Unless you have had a past choking experience, rarely would you worry about choking. Chewing and swallowing are second nature but have you ever stopped to think about what it took to reach the level of efficiency you have now? While the act of swallowing is an involuntary and automatic reflex, the act of chewing is a learned skill that is dependent on the type of feeding experiences a child is exposed to. With repeated practice and opportunities to chew various textures of food, chewing moves from a highly conscious act to an unconscious act as motor pathways are built and solidified through motor memory.
So how exactly did we learn these intricate skills? In a future blog post, we will dive into the neurobiological development of feeding from the womb up to early childhood. In the meantime, I encourage you to engage in the attached mindfulness eating exercise below to bring your attention to the intricacies of chewing and swallowing.
