Читать книгу The Esophagus - Группа авторов - Страница 126

The UES is highly responsive to a number of pharyngeal and esophageal events that either increase UES pressure or relax the sphincter. These reflexes, mediated by vagal afferents, protect the airway from esophageal content or release esophageal content during belching or vomiting [17, 46, 104, 112].

Esophageal distention with air, liquid, or balloons can either increase or decrease UES pressure, depending on the volume and rapidity of distention [101, 112]. Slow distention causes a protective augmentation in UES pressure [112, 113]; the pressure is augmented as distension increases [78, 114], and with closer proximity to the UES [112, 115]. Rapid distention and large distension volumes result in UES relaxation, with glottis closure and esophageal belching when air is introduced [116, 117]; there is a linear correlation between duration of UES relaxation and the volume of air introduced. The belch is also associated with glottic closure. UES relaxation also occurs with vomiting, a gastric belch, and rumination.

Acid in the esophagus increases UES pressure, with more profound increases when acid is infused closer to the UES or at the UES [112, 114, 118], but this reflex may be less prominent in humans compared to dogs, especially patients with esophagitis. Infusion of acid 5 cm below the UES in normal subjects [119], and acid reflux into the distal esophagus in normal subjects and in patients with esophagitis, did not increase UES pressure [120]. Increases in intrathoracic pressure with gagging or Valsalva maneuver increase UES pressure.

Figure 5.8 Muscular architecture of the pharynx and upper esophagus from the laterodorsal aspect. The cricopharyngeus muscle has an upper portion that is continuous with the inferior constrictor muscle and a lower portion that encircles the region at the approximate location of the highest upper esophageal sphincter pressure. Between the two portions is a small space, the Killian triangle, where a Zenker’s diverticulum will occur. The lower border of the cricopharyngeus and the origins of the longitudinal layer of the upper esophageal striated muscle form another triangle, Laimer’s triangle.

Source: Liebermann‐Meffert [80] with permissions of Oxford University Press.

Pharyngeal stimulation with small volumes of water, 0.1–1.5 cm, will induce the oropharyngeal stage of swallowing with UES relaxation. However, prior to initiation of the swallow, UES pressure increases [13].