Читать книгу The Esophagus - Группа авторов - Страница 18

The mechanism underlying esophageal pain and discomfort is not well defined, but patient symptoms likely develop as a result of a complex neurophysiologic response to a stimulus on a nociceptor. The esophagus is dually innervated by involuntary parasympathetic (vagal) and sympathetic (spinal afferent) nerves [5]. Vagal nerve cell bodies originate in the medulla. Those within the nucleus ambiguous control skeletal muscle while those within the dorsal motor nucleus control smooth muscle. Efferent nerves from the medulla terminate directly on the motor endplate of upper esophageal skeletal muscle, while efferent nerves directed toward distal esophageal smooth muscle terminate in the myenteric plexus, which is located between the longitudinal and circular muscle layers [6].

Afferent impulses from the esophagus heading toward the spinal cord and brain are typically triggered by the stimulation of a variety of nociceptors within the esophagus. Different chemoreceptors, thermoreceptors, and mechanoreceptors have been identified in the esophageal mucosa, submucosa, and musculature [7]. The sensation of pain is often triggered by chemoreceptor or mechanoreceptor stimulation, as these nociceptors are sensitive to intraluminal distension. Since both vagal and spinal nerves innervate the esophageal mucosa, these afferents are also sensitive to touch, pH, and chemical irritation [5].

The superior laryngeal nerves, recurrent laryngeal nerves, and vagal branches within the esophageal plexus all carry their parasympathetic afferents signals to the vagus nerve, which then carries them on to the brainstem. The splanchnic nerves carry their sympathetic spinal afferent signals to the spinal cord and on to the thalamus [5]. Central perception of symptoms then occurs when these impulses arrive in the brain, either by myelinated fibers that carry pain sensations rapidly and result in sharp, localized pain, or by unmyelinated C‐fibers that transmit impulses more slowly and lead to duller, poorly localized symptoms [8, 9]. These neuroanatomic esophageal pathways are also complex in that they overlap with those of the heart and lungs, as the vagal afferents from all three organs converge prior to their transmission to higher processing centers in the brain. It is for this reason that it can be challenging to discern the anatomic origin of certain symptoms, such as chest pain.