The esophagus is a muscular tube approximately 25 cm long that extends from the neck down the posterior mediastinum and through the diaphragm to the stomach (Figure 37-1). It is lined by nonkeratinizing stratified squamous epithelium that transforms abruptly to gastric epithelium at the gastroesophageal junction. The junction is usually 37–40 cm from the incisor teeth and may be identified endoscopically by a change in appearance from the white squamous mucosa to the tan glandular mucosa.
Structure and function of the esophagus.
The esophagus has physiologic high-pressure zones at either end that act as sphincters. There is no anatomic sphincter at either end. The upper cricopharyngeal sphincter prevents entry of air and pharyngeal contents into the esophagus except during swallowing, and the lower esophageal or “cardiac” sphincter prevents reflux into the esophagus of acidic gastric juice.
Deglutition (swallowing) is a reflex that is initiated when a bolus of food stimulates nerve endings in the mucosa of the posterior pharyngeal wall (Figure 37-1). Efferent impulses from the deglutition center in the brain stem cause pharyngeal muscle contraction and relaxation of the cricopharyngeal sphincter, permitting entry of food into the esophagus and initiating peristalsis.
Peristalsis consists of successive waves of contraction preceded by relaxation of the esophageal muscle, which propels food down the esophagus. Peristaltic action is coordinated by the myenteric plexus of nerves. Three types of peristaltic waves are recognized: (1) primary waves, which originate in the lower pharynx and pass down the entire esophagus; (2) secondary waves, which originate in the mid esophagus and pass down to the stomach; and (3) tertiary waves, which are irregular contractions of segments of the wall. Primary and secondary waves are propulsive; tertiary waves are nonpropulsive. The lower esophageal sphincter relaxes when a propulsive peristaltic wave (either primary or secondary) reaches the lower esophagus, permitting food to enter the stomach (Figure 37-2).
Motility patterns in normal (A) and abnormal (B–E) esophagi. Normally (A), the upper and lower esophageal sphincters have an increased pressure. Swallowing produces a wave of contraction down the esophagus, with synchronized sphincter relaxation. In skeletal muscle diseases (C) (eg, myopathy, polymyositis), striated muscle abnormality results in failure of upper esophageal and pharyngeal contraction. In progressive systemic sclerosis (B), lower esophageal peristalsis is abnormal and the lower esophageal sphincter resting pressure is low because of muscle replacement. In achalasia (D), peristalsis is abnormal in the low esophagus but lower esophageal sphincter pressure is high and fails to come down to baseline with swallowing. In diffuse esophageal spasm (E), there are high-amplitude simultaneous contractions in the lower esophagus.
Dysphagia simply means difficulty in swallowing. The patient often complains that food “gets stuck” without passing down normally. ...