<prompt> Most common site of peptic ulcer in duodenum -1st pa2d pa3rd pa4th pa  <response>: Ans. is a i.e., 1st paPeptic ulcero Ulcers are defined histologically as a breach in the mucosa of the alimentry tract that extends through themucularis mucasea into the submucosa or deep.o Peptic ulcers are chronic , most often solitary lesions that occur in any protion of the gastrointestinal tract exposedto the aggressive action of acid peptic juice .Peptic ulcers located in the following sits, in order of decreasing frequency : Duodenum, 1 poionStomach ,usally antrumAt the gastro - esophageal junction in the setting of gastroesphageal reflux or Barretts esophagus.Within the margins of a gastrojejunostomy.In the duodenum, stomach or jeunum of patients with Zollinger -Ellison Syndrome.Within or adiacent to Meckels diveiculum that contains ectopic gastric mucosa. 