Peptic ulcers develop when the stomach's protective lining is weakened — most often by H. pylori infection or chronic use of anti-inflammatory medications. This erosion exposes the tissue underneath to powerful stomach acid. When the ulcer reaches a blood vessel, it begins to bleed — sometimes slowly, sometimes with life-threatening hemorrhage. Symptoms can include abdominal pain, vomiting blood, or black stools. This animation shows a bleeding gastric ulcer, based on SciePro’s 3D anatomy model.