Maturation of the lower esophagus.
D000367:Age Factors; D001835:Body Weight; D004947:Esophagus / Q000033:anatomy & histology / Q000502:physiology*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D011247:Pregnancy; D011312:Pressure