Surgical myotomy of the cricopharyngeus does not abolish UES tone. 7 UES location can be determined by side-port catheters for the purpose of placing proximal esophageal pH electrodes. 3 Primary peristalsis begins after swallowing, in coordination with pharyngeal contraction and UES and LES relaxation. Secondary peristalsis occurs secondary to intraluminal distention, usually by the food bolus. This function is important in esophageal clearance of material such as refluxed gastric contents.
Tertiary contractions consist of random, spontaneous contractions that have no peristaltic function.
Pressures within the esophageal body vary with respiration. The velocity of esophageal contractions is typically from 2 to 5 cm per second but is slower during the first week of life, ranging from 0.8 to 2 cm per second. The LES is the high-pressure zone between the esophageal body and the stomach. Like the UES, its length increases with age, from 1 cm in the newborn to 2-5 cm in the adult. 10,11 LES pressure also varies with age, ranging from 7 mm Hg in a premature infant of 27 weeks gestation to 18 mm Hg at term and from 10 to 45 mm Hg in the adult.