Physiology of the upper segment, body, and lower segment of the esophagus

Abstract

The following discussion on the physiology of the esophagus includes commentaries on the function of the muscularis mucosa and submucosa as a mechanical antireflux barrier in the esophagus; the different mechanisms of neurological control in the esophageal striated and smooth muscle; new insights from animal models into the neurotransmitters mediating lower esophageal sphincter (LES) relaxation, peristalsis in the esophageal body (EB), and motility of esophageal smooth muscle; differentiation between in vitro properties of the lower esophageal circular muscle, clasp muscle, and sling fibers; alterations in the relationship between pharyngeal contraction and relaxation of the upper esophageal sphincter (UES) in patients with dysphagia; the mechanical relationships between anterior hyoid movement, the extent of upper esophageal opening, and aspiration; the application of fluoroscopy and manometry with biomechanics to define the stages of UES opening; and nonpharmacological approaches to alter the gastroesophageal junction (GEJ).

Keywords: GERD; esophagus; lower esophageal segment; muscularis mucosa; smooth muscle; submucosa; upper esophageal segment.

Figure 1

Endoluminal ultrasound and manometry and transabdominal ultrasound of the distal esophagus and proximal stomach in normal control subjects.

Figure 2

EFS-induced responses on human esophagus. (A) Electrical field stimulation–induced responses at different frequencies in both clasp and sling regions of the lower esophageal sphincter (LES) and the esophageal body (EB). (# # P < 0.01 clasp vs. sling fibers; Ø P < 0.05 EB vs. clasp LES; † P < 0.05 EB vs. sling LES). Agonist-induced responses on human esophagus. (B) Concentration-response curves for carbachol (CCh, middle graph) and sodium nitroprusside (SNP, right graph) in the clasp and sling muscles of human LES and EB. (Ø P <0.05 EB vs. clasp LES; † P <0.05 EB vs. sling LES).

Figure 3

Diagrams illustrating the major differences in the neuromuscular control of contraction and relaxation between clasp and sling fibers of the human upper gastric sphincter.

Figure 4

Patterns of coordination between thyroarytenoid contraction and cricopharyngeal relaxation during swallowing that may affect risk of aspiration. (A) a delay in the onset of thyroarytenoid activity after the cricopharyngeus relaxation occurs; (B) overlap of activity of thyroarytenoid and relaxation of cricopharyngeus; and (C) increased activity in the thyroarytenoid before the pause in cricopharyngeus electrical activity. Adapted from Ref. .

Figure 5

Six lateral videofluoroscopy images over a 2-s period in a 54-year-old male with oropharyngeal dysphagia poststroke swallowing a liquid bolus. Note timer display in hours: minutes: seconds: frames (25 frames per second). (A) Liquid barium bolus passes to the level of the pyriform sinuses before the pharyngeal swallow has been initiated. Note (i) UES remains closed; (ii) hyoid bone and larynx are in resting position; and (iii) airspace is evident between tongue base and posterior pharyngeal wall. (B) Pharyngeal swallow is initiated. Hyoid bone is being pulled anteriorly and superiorly toward mandible due to suprahyoid and thyrohyoid muscle contraction. Tongue base begins to retract toward posterior pharyngeal wall to propel bolus through UES. UES has not yet opened. (C) UES opens (49.21) and bolus begins to pass into the esophagus. (D) Material continues to pass through the UES. (E) UES closes (50.06). UES opened for 10 frames (0.40 s). (F) Residue in valleculae and pyriform sinuses observed postswallow. Penetration of barium is visible to the level of the vocal cords.