One of our most fundamental needs for survival is nutrition. The most natural way of obtaining nutrition is by taking food orally and swallowing it so that it reaches the stomach and intestinal system. In addition, we regularly swallow our saliva approximately 1,000 times a day.

Swallowing is a complex process that begins voluntarily and continues involuntarily (reflexively). This complex process occurs in four distinct phases: the oral preparatory phase, oral phase, pharyngeal phase, and esophageal phase.

Oral preparatory phase: During this phase, food is taken into the mouth, chewed, and formed into a bolus (a small rounded mass suitable for swallowing).

Oral phase: This phase begins with the backward movement of the bolus toward the pharynx. The oral transit time is approximately 1–1.5 seconds.

Pharyngeal phase: A very rapid phase, the pharyngeal phase occurs reflexively. To protect the airway, the soft palate elevates, and the larynx moves forward and upward; the laryngeal inlet and vocal folds close to prevent food from entering the airway. The transit of the bolus through the pharynx takes only one second.

Esophageal phase: This phase begins as the bolus enters the esophagus and is transported to the stomach within approximately 8–20 seconds.

What is Swallowing Disorder (Dysphagia)?

Any impairment in the swallowing process described above is referred to as a swallowing disorder, medically known as dysphagia. Dysphagia encompasses all types of swallowing difficulties that may occur during eating and drinking. Problems, delays, or obstructions can occur at any stage—from food preparation in the mouth to its passage from the oral cavity to the stomach. Additionally, food or liquids may sometimes enter the esophagus incorrectly and accidentally pass into the airway.

In healthy individuals, the laryngeal inlet and vocal folds close completely during swallowing, preventing any food or liquid from entering the airway. The entry of food or liquid into the upper laryngeal region, up to the vocal folds, is called penetration, whereas passage below the vocal folds into the airway is referred to as aspiration.

Aspiration is a serious condition as it means food or liquids enter the airway and reach the lungs. This can lead to lung infections and, in severe cases, may even be life-threatening.