Physiologic Aspects Of Esophageal Function

The act of alimentation requires the passage of food and drink from the mouth into the stomach. One third of this distance consists of the mouth and hypopharynx, and two thirds consist of the esophagus. To comprehend the mechanics of alimentation, it is useful to visualize the gullet as a mechanical model in which the tongue and pharynx function as a piston pump with three valves, and the body of the esophagus and cardia function as a worm drive pump with a single valve. The three valves in the pharyngeal cylinder are the soft pallet, the epiglottis, and the cricopharyngeus. The valve of the esophageal pump is the lower esophageal sphincter. Failure of the valves or the pumps leads to abnormalities in swallowing—that is, difficulty in the propulsion of food from the mouth to the stomach or the regurgitation of gastric contents from the stomach into the pharynx.

Food is taken into the mouth in a variety of bite sizes, where it is broken up, mixed with saliva, and lubricated. Swallowing, once initiated, is entirely a reflex. When food is ready for swallowing, the tongue, acting like a piston, moves the bolus into the posterior oropharynx and forces it into the hypopharynx ( Fig. 6-1 ). Concomitant with the posterior movement of the tongue, the soft palate is elevated, thereby closing the passage between the oropharynx and nasopharynx. This partitioning prevents pressure generated in the oropharynx from being dissipated through the nose. When the soft palate is paralyzed, as occurs after a cerebrovascular accident, the food is commonly regurgitated into the nasopharynx. During swallowing, the hyoid bone moves upward and anteriorly, elevating the larynx and opening the retrolaryngeal space. This brings the epiglottis under the tongue ( Fig. 6-1 ). The backward tilt of the epiglottis covers the opening of the larynx to prevent aspiration. The entire pharyngeal part of swallowing occurs within 1.5 seconds.

The pressure in the hypopharynx rises abruptly during swallowing to reach at least 60 mmHg. A sizable pressure difference develops between the pharyngeal pressure and the less-than-atmospheric midesophageal or intrathoracic pressure ( Fig. 6-2 ). This pressure gradient speeds the movement of food from the hypopharynx into the esophagus

Figure 6-1 Sequence of events during the oropharyngeal phase of swallowing.

Figure 6-1 Sequence of events during the oropharyngeal phase of swallowing.

Figure 6-2 Resting pressure profile of the foregut showing the pressure differential between the atmospheric pharyngeal pressure (P), and the less than atmospheric midesophageal pressure (E), and the greater than atmospheric Intragastric pressure (G), with the Interposed high pressure zones of the cricopharyngeus (C) and distal esophageal sphincter (DES). The necessity for coordinated relaxation of the cricopharyngeus and DES in order to move a bolus into the stomach is apparent. Esophageal work occurs when a bolus is pushed across the pressure gradient from the midesophageal area (E) into the stomach (G). (From Waters, P.P., and DeMeester, T.R. : Foregut motor disorders and their surgical management. Med. Clin. North Am., 65:1237, 1981, with permission.)

Figure 6-2 Resting pressure profile of the foregut showing the pressure differential between the atmospheric pharyngeal pressure (P), and the less than atmospheric midesophageal pressure (E), and the greater than atmospheric Intragastric pressure (G), with the Interposed high pressure zones of the cricopharyngeus (C) and distal esophageal sphincter (DES). The necessity for coordinated relaxation of the cricopharyngeus and DES in order to move a bolus into the stomach is apparent. Esophageal work occurs when a bolus is pushed across the pressure gradient from the midesophageal area (E) into the stomach (G). (From Waters, P.P., and DeMeester, T.R. : Foregut motor disorders and their surgical management. Med. Clin. North Am., 65:1237, 1981, with permission.)

Figure 6-3 Intraluminal esophageal pressures in response to swallowing. (From Waters, P.F., and DeMeester, T.R.: Fore gut motor disorders and their surgical management. Med. Clin. North Am., 65:1238, 1981, with permission.)

Figure 6-4 Schematic drawing showing wall thickness and orientation of fibers on mlcrodis-section of the cardia: At the junction of the esophageal tube with the gastric pouch, there is an oblique muscular ring composed of an increased muscle mass inside the inner muscular layer. On the lesser curve side of the cardia the muscle fibers of the inner layer are oriented transversely and form semicircular muscle clasps that insert into the submucosal connective tissues. On the greater curve side of the cardia, these muscle fibers form long oblique loops that run parallel to the lesser curve of the stomach and encircle the distal end of the cardia and gastric fundus. (From DeMeester, T.R., and Skinner, D.B.: Evaluation of esophageal function and disease. In Glenn, W.W.L. [ed.]: Thoracic and Cardiovascular Surgery, 4th ed. Norwalk, CT, Appleton-Century-Crofts, 1983, p. 461, with permission.)

Was this article helpful?

0 0
Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

Get My Free Ebook


Responses

  • Dr Kenneth Sylvester
    what is distance between cricopharyngeus and midesophagus
    8 years ago

Post a comment