Prostaglandin is one of the impoant defensive mechanism against erosion of the gastric mucosa. Impaired production of PG will result in peptic ulcer formation. Defensive mechanisms may be divided into anatomic and physiologic types. Anatomic mechanisms are adequate blood supply, proper tight junctions between epithelial cells etc. Physiologic mechanisms include production of mucus, PG, bicarbonate into the mucus etc. Regenerating capacity of epithelial cells also play an impoant role against the formation of peptic ulcer. Ref: Dohey G.M., Way L.W. (2010). Chapter 23. Stomach & Duodenum. In G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13e.