The Ins, Outs, and In Betweens of Your Digestive Tract: How Muscle Imbalances in Your Jaw and Neck Affect Digestion – Part Two: Swallowing
You know the feeling of having your omega-3 capsule stick to the walls of your esophagus and lodge there until you drink more water or eat a piece of breath to shove it down? An object’s progress from mouth to stomach is an intricate dance of body position and muscle function. Now that you have been able to ruminate about chewing (See Part One: Chewing if you missed it), it’s time to move on to swallowing and how our habitual head position changes the reflex.
Remember, the digestive tract is a tube of smooth muscle that travels from the mouth to anus. Movement through most of the canal is achieved through peristalsis, or wave-like contractions of the tube walls. Skeletal muscles assist in areas of the tract where food needs to be propelled, like swallowing in the throat.
The skeletal muscles of swallowing are the geniohyoid, mylohyoid, and stylohyoid, collectively known as the suprahyoids. They form a sling of muscles along the underside of the jaw. They span from the anterior, inner edge of the mandible to the hyoid bone. The hyoid bone is a horseshoe shaped bone that floats between the root of the tongue and cartilage of the voice box. Their roles are to depress the mandible and to elevate the hyoid and tongue for swallowing.
Normal swallowing is a complex voluntary and reflexive process involving the tongue and sequential contraction of these muscles. Swallowing happens in four stages. As we chew our food, our tongue moves it around our mouth so it can be crushed and mixed with saliva. This forms a bolus, or round bundle of food ready for swallowing. In the first phase of swallowing, the tongue pushes the food mash toward the back of our throat. This is followed by the propulsion of the food into the upper pharynx through further contraction of the tongue. In the third stage, the bolus is transported through the pharynx and esophageal sphincter by synchronized muscular contraction of the suprahyoid muscles. Their action pulls the hyoid bone and voice box up and forward to open the entrance to the esophagus.