10.6: Esophagus

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The esophagus is a tube that transports materials from the pharynx to the stomach (Figure 10.1). During swallowing, peristaltic muscular contractions in the esophagus push materials into the stomach (Figure 5.6). Coordinated contractions of the muscles are reflexively controlled by a network of nerve cells (Auerbach's plexus) in the wall of the esophagus. Since this network extends from the esophagus to the end of the large intestine, it can coordinate many functions throughout the GI tract.

Age Changes

Aging causes esophageal peristalsis to become slightly slower and weaker. This change seems to be caused by aging of neurons in Auerbach's plexus. The result is an increase in the frequency with which materials do not pass into the stomach as fast as usual or pass from the stomach up into the esophagus and cause discomfort, which may be experienced as heartburn.

Abnormal Changes

Esophageal Rings and Webs

Though the esophagus normally functions well throughout life, many older people develop abnormalities such as the formation of esophageal rings and webs. These growths project inward from the wall of the esophagus and partially block the passage through the esophagus, causing difficulty swallowing.

Strictures

A second abnormality is the formation of strictures, which are rings of scar tissue that develop from repeated injury to the esophagus. One cause of such injury is repeated passage of stomach contents into the esophagus. A stricture blocks the esophagus because the collagen in the scar tissue gradually shrinks, resulting in a narrowing of the passage through the esophagus and difficulty swallowing.

Sliding Hiatal Hernia

A third structural abnormality of the esophagus is sliding hiatal hernia. In this condition, the connection between the esophagus and the stomach slips above the diaphragm rather than remaining in its normal position below the diaphragm. The incidence of sliding hiatal hernia increases with age, and up to 70 percent of those over age 70 develop this disease. Most cases result from alterations in esophageal muscles and decreased elasticity of the diaphragm.

Other Abnormalities

A fourth cause of abnormal esophageal functioning is diabetes mellitus. Diabetes substantially slows peristalsis in the esophagus and all other parts of the GI tract. Other abnormalities that disturb esophageal functioning include nervous system diseases (e.g., strokes), alcoholism, medications, and cancer.

Effects and Complications

Abnormalities in the esophagus can result in a variety of esophageal malfunctions. For example, peristalsis may not begin during swallowing, or it may be very slow or uncoordinated or occur with spasms. Each of these situations or partial blockage of the esophagus will inhibit the movement of materials down the esophagus and into the stomach. Two results are mild to severe discomfort and difficulty eating. Food selection may be limited, and completing a meal may take an inordinate amount of time. In addition, medications that fail to travel through the esophagus quickly can injure the esophagus. Finally, esophageal malfunction can allow stomach contents to flow upward and into the esophagus, a process called gastric refluxing. Since the stomach contains strong acids, this can cause pain, ulcers, and bleeding in the esophagus as well as esophageal strictures. Sometimes stomach contents may enter the respiratory passages through the larynx, causing hoarseness, inflammation of the respiratory system, or death.

For some photos of digestive system diseases, go to Preserved Specimen Photos and to Microscope Slides.
For Internet images of normal digestive system structures or diseases, search the Images section of http://www.google.com/ for the name of a particular structure or disease. For diseases, I highly recommend searching WebPath: The Internet Pathology Laboratory , the excellent complete version of which can be purchased on a CD.

Prevention and Treatment

The frequency and severity of the adverse effects of esophageal malfunctioning can be reduced in several ways. The head and trunk can be kept slightly elevated so that the force of gravity assists in swallowing and helps prevent gastric refluxing. Avoiding large meals or obesity results in the same benefits because pressure in the abdomen is kept low. Other methods to reduce gastric refluxing include; avoiding foods and medications known to increase stomach acid and gastric refluxing; using medications that promote esophageal clearance, coat the esophagus, or reduce gastric refluxing; using antacids to reduce stomach acidity; and undergoing surgical correction of structural abnormalities.