<prompt> Which of following is not a permanent mucosal fold?Spiral valve of HeisterGastric rugaePlica circularisTransverse rectal fold  <response>: Gastric rugae of the stomach and longitudinal folds in the mucosa of upper rectum and colon are temporary mucosal folds and are obliterated by distension. Whereas, plica circularis of the small intestine, crescentic mucosal folds of cystic duct spiral valve of Heister, transverse horizontal rectal folds Houstons valves or plica transversalis and permanent longitudinal rectal columns or folds found in the lower rectum and anal canal are permanent mucosal folds. 