Swallowing, or deglutition, involves the tongue, pharynx, and esophagus in three phases: oral, pharyngeal, and esophageal. Cranial nerves play important roles in each phase. Swallowing disorders can occur due to various factors, with dysphagia and odynophagia being common symptoms.
Swallowing is the scientific term for the word swallowing. It comes from the Latin word deglutire, which means “to swallow”. The muscles of the tongue, pharynx and esophagus are involved in the swallowing process, which is divided into three phases: the oral phase, the pharyngeal phase and the esophageal phase. The cranial nerves also play many important roles in these stages.
The oral phase is usually a voluntary phase, which means that it is often done consciously by the individual. It starts when food enters the mouth. Through the process of mastication, or mastication, food is broken into smaller pieces. Then the tongue pushes the pieces of food towards the pharynx, or behind the throat. The cranial nerves involved during the oral phase are the trigeminal nerve, the facial nerve and the hypoglossal nerve.
As soon as the food reaches the back of the throat, the pharyngeal phase occurs, which is mostly involuntary. The uvula and soft palate usually block the passage of food to the nose by covering the nasopharynx, which opens to the nasal passages. At the same time, the swallowing reflex begins pushing foods up the esophagus and away from the lungs with the help of the epiglottis, which is a flap of tissue that covers the larynx. During this process, swallowing apnea occurs, which means that breathing stops for a very short time. Cranial nerves involved during this stage include the vagus, accessory, and hypoglossal nerves.
The esophageal phase, which also occurs involuntarily, begins with the opening of the esophageal sphincter to let food in. When food reaches the end of the esophagus, another muscle, called the cardiac sphincter, opens to pass food to the stomach for digestion. A sphincter is a ring of muscle that contracts and relaxes and prevents or allows materials to pass from one area to another, such as between the esophagus and the stomach.
Swallowing disorders sometimes occur in the elderly, especially after a stroke. Because the cranial nerves are often affected in stroke patients, food particles can sometimes enter their lungs and cause infections. Any birth defect, infection, obstruction, injury, or cancer growth in the pharynx or esophagus can affect the swallowing process. The most common symptom of a swallowing disorder is dysphagia or difficulty swallowing. Another symptom is odynophagia, or pain when swallowing.
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