Sväljningsfaserna

Sväljningsfaserna, or swallowing phases, refer to the distinct stages involved in the complex physiological process of moving food or liquid from the mouth to the stomach. This process is crucial for nutrition and preventing aspiration, which is the entry of foreign material into the airway. Swallowing is typically divided into three or four phases, depending on the classification system used.

The first phase, the oral preparatory phase, is voluntary. During this phase, food is manipulated in the mouth, chewed (if solid), and mixed with saliva to form a bolus. The tongue is active in positioning the food and preparing it for transport.

The second phase, the oral propulsive phase, is also voluntary. The tongue thrusts the bolus posteriorly towards the pharynx. This action triggers the involuntary phases of swallowing.

The third phase, the pharyngeal phase, is involuntary and rapid. As the bolus enters the pharynx, the soft palate elevates to seal off the nasal cavity, and the epiglottis covers the larynx to protect the airway. The pharyngeal muscles contract to propel the bolus downwards. Breathing is temporarily inhibited during this phase.

The fourth phase, the esophageal phase, is involuntary. Once the bolus passes the upper esophageal sphincter, it enters the esophagus. Peristalsis, a series of wave-like muscular contractions, moves the bolus down the esophagus towards the stomach. The lower esophageal sphincter relaxes to allow the bolus to enter the stomach. Disruptions in any of these phases can lead to dysphagia, or difficulty swallowing.