<prompt> The most common site of peptic ulcer in duodenum -1st part2nd part3rd part4th part  <response>: Ans. is a i.e., 1st part Peptic ulcero Ulcers are defined histologically as a breach in the mucosa of the alimentary tract that extends through the muscular mucosa into the submucosa or deep.o Peptic ulcers are chronic, most often solitary lesions that occur in any portion of the gastrointestinal tract exposed to the aggressive action of acidpeptic juice.Peptic ulcers located in the following sits, in order of decreasing frequency:1.Duodenum, 1st portion2 Stomach, usually antrum3 At the gastroesophageal junction in the setting of gastroesophageal reflux or Barretts esophagus.4 Within the margins of a gastrojejunostomy.5 In the duodenum, stomach or jejunum of patients with Zollinger -Ellison Syndrome.6 Within or adjacent to Meckels diverticulum that contains ectopic gastric mucosa. 