Development of esophageal function.

There is limited information on the developmental aspects of esophageal motor function in humans. Length of the esophageal body and its sphincters increases progressively after birth. The UES is well developed at birth, and except for a slight pressure increase during the first year, there is little evidence of functional maturation postnatally. Within the esophageal body, the sucking and swallowing patterns mature within a few days in term infants, whereas this maturation takes longer in premature infants. In the LES, pressures may be low at birth but thereafter rise above adult levels until 6 months of age, to slowly decrease to adult levels by 1 to 3 yr of age. Maturation of the LES reflects at least an increase in bulk, although neural maturation and maturation of muscle responsiveness require further assessment in humans. The relationship of LES dysfunction to gastroesophageal reflux in infants is still not elucidated. The relationship of gastroesophageal reflex to pulmonary problems is similarly uncertain.