Digestive System

Swallowing, or deglutition, is an important step in getting the bolus to our stomach. When we are ready to swallow the bolus, we place the bolus on the surface of our tongue. The front part of the tongue touches the area in our mouth just behind the upper front teeth. Then more parts of the tongue touch the roof of the mouth, starting with the area closest to the front teeth and ending with the area closest to the pharynx. This causes the food to move from the front of the mouth to the back of the mouth. Depending on whether we have more food that needs to be chewed in our mouth, we may alternate between chewing the food and swallowing it.

As the food goes into the back of the mouth, the soft portion of the roof of the mouth lifts up  and seals the sides and the back of the pharynx so that the bolus does not go into the nose. The base of the tongue (ie, where it attaches to the floor of the mouth) pulls back and pushes the food against the walls of the pharynx. The muscles of the pharynx contract in a wavelike sequence, starting with the muscles in the upper part of the pharynx and ending with the muscles in lower part of the pharynx. This forces the bolus downward.

The cartilage to which the vocal cords are attached in the larynx, or voicebox, tilt forward to touch the base of the epiglottis and the epiglottis flips downward to cover the larynx. The vocal folds, which are at the top of the larynx, tighten so that the space between them is closed. The muscles that attach to the hyoid bone contract, which forces the hyoid bone and the larynx upward and backward. This also moves the larynx under the base of the tongue. The pharynx itself also shortens. These measures decrease the chances of food entering the trachea.

When we are ready to swallow liquids, we move the tip of our tongue to a ridge in the upper part of our mouth just behind our upper front teeth. This causes the back of our tongue to drop down, which breaks the seal that the tongue helped to create.   The surface of the tongue then moves upward along the top of our mouth from front to back and more areas of the tongue come into contact with the roof of the mouth. This forces the liquid to the back of the mouth.  The soft portion of the roof of the mouth moves up and covers the sides and the back of the pharynx. This forms a seal that prevents liquids from entering the nose.

When we drink liquids, the liquid is held in the front, lower part of the mouth or on the tongue against the teeth and the hard palate. The soft palate and the tongue form a seal to prevent the liquid from going into the pharynx before we are ready to swallow it, which does not happen when we eat foods.