Читать книгу The Esophagus - Группа авторов - Страница 120

A liquid bolus moves quickly along the pharynx from tongue thrust and gravity, prior to the slower peristaltic contraction of the three pharyngeal constrictor muscles [69, 70]. The larger the bolus, the quicker it moves; tongue force and shape change to accommodate bolus size [71]. Solid boluses, in contrast, rely on peristaltic contraction for passage and clearance. Pharyngeal peristalsis starts within less than 0.5 s, with the pressures showing radial and axial asymmetry [72, 73]. The 1 s timing of the process to clearance of either liquid or solid is not altered much by bolus consistency or size [71, 74, 75], and pharyngeal peristaltic velocity remains constant.

Protection of the nasal cavity

As the bolus enters the pharynx, the soft palate moves upward and backward to meet concurrent upper constrictor muscle contraction, producing a ridge in the posterior pharyngeal wall called Passavant’s ridge [67, 76]. These actions close the nasopharynx. The contraction of the posterior pharyngeal wall proceeds distally through the pharynx, and the palate remains elevated until the larynx descends [71].