Читать книгу The Esophagus - Группа авторов - Страница 119

The pharynx is an irregular muscular tube, with the superior, middle, and inferior constrictor muscles supported by cricoid cartilage and the epiglottis [58, 59]. The oropharynx is the upper portion of the pharynx, between the soft palate and the tongue, extending to the valleculae and tip of the epiglottis, and to the nasopharynx superiorly. The remainder of the pharynx, the hypopharynx, extends from the valleculae to the bottom of the cricoid cartilage. The pyriform sinuses are situated laterally between the insertion of the inferior constrictor and the lateral wall of the thyroid cartilage; they end at the cricopharyngeus muscle and add to the axial and radial asymmetry of the pharynx. The hyoid bone forms the attachment location for a number of muscles that raise and lower the larynx. The upper esophageal sphincter, formed primarily by the cricopharyngeus muscle, operates closely with the pharynx.

Masticating, forming the food bolus, and positioning it on the tongue for the swallow involves the lips, teeth, hard and soft palates, floor of the mouth, mandible and tongue, and associated muscles. During mastication, the posterior tongue is elevated and the soft palate pulled down against the tongue to prevent spillage into the pharynx, although some leaking of oral content does occur [60]. Jaw‐closing and jaw‐opening muscles of mastication coordinate with each other and shift to the swallowing reflex when mastication ends and swallowing begins, likely under central control [61]. Voluntary triggering of swallows occurs >100 milliseconds before the onset of the swallowing reflex, while this interval is <50–100 milliseconds in reflexive swallows [1]. Once the swallow is initiated, the bolus is rapidly thrust into the pharynx by the tongue, following which the involuntary oral, pharyngeal, and esophageal stages of the SPG‐controlled program are initiated. This results in a series of rapid and highly coordinated events that take less than a second to complete: closure of the nasopharynx, elevation of the entire soft pharynx and the UES to protect the airway, opening of the UES, and a propulsive contraction to clear the pharyngeal content. Respiration is halted to temporarily switch the pharynx from a respiratory to an alimentary configuration [2, 54, 62]. Oropharyngeal dysphagia and/or aspiration can occur if any portion of the process fails or becomes abnormal, such as with neurologic or muscle disorders [63–65]. The timing of the symptom within a second of swallow initiation is often a clue that pathophysiology lies in the oropharyngeal stage of swallowing.

Figure 5.3 shows the multitude of muscles involved in different functions of the pharyngeal swallow. Figures 5.4 and 5.5 illustrate the timing of some of the events and the typical X‐ray pattern seen as they occur. Videofluoroscopic examination is the most common method of assessing oropharyngeal swallowing [66]. Computed imaging techniques used to assess tongue muscle function are not practical clinical tools [67, 68]. High‐resolution manometry (HRM) provides precise evaluation of pharyngeal and UES physiology and pathophysiology (Figure 5.6). The clinical value of these measurements continues to be investigated.