DAZLEY, J.S.; FARMER, C.G.; MOORE, J; CLAYTON, F.; University of Utah; University of Utah; Veterans Administration Hospital; Veterans Administration Hospital: Esophageal Structure and Function in the American alligator

An appreciation of the usefulness of reptiles as model organisms to study regulatory physiology of the gastrointestinal system is increasing. In contrast to most mammals, that generally eat relatively small meals at frequent intervals, many carnivorous reptiles consume extremely large meals infrequently. Thus, the regulatory responses to feeding can be very pronounced in reptiles compared to mammals. Furthermore, reptiles do not provoke the same level of controversy surrounding animal research that mammals do. Recent research on the reptilian gastrointestinal system has focused on responsed to feeding that occur in the lower gastrointestinal tract. Relatively little recent work has examined the upper GI tract. For these reasons, we undertook a study of esophageal structure and function in the American alligator. Five juvenile, () weighing 0.431 � 0.09 kg. (S.E.M.) were studied. Pressure was measured at 22�C along the esophagus. Peristaltic waves had a speed of 206.815 � 4.1 m/s (S.E.M.). Furthermore, we found a high-pressure zone of the esophagus located cephalad to the stomach, which indicated the presence of a lower esophageal sphincter. Histological analyses of longitudinal sections of the esophagus revealed the presence of cilia, similar to that found in the respiratory tract of mammals. There was no striated muscle present, but we did see the expected longitudinal and circular layers of smooth muscle, muscularis mucosa, a myenteric nerve plexus, mucus secreting goblet cells, a cuboidal epithelial layer and evidence of an enteric nervous system.