Echinocytes in gastric ulcer. Coloured scanning electron micrograph (SEM) of abnormal red blood cells (echinocytes) at the site of a human gastric ulcer. Echinocytes are red blood cells which become sea urchin shaped" from their normal smooth biconcave surface. They develop a spiked, crenated edge due to a plasmolysis reaction. Echinocytes may form at sites of medical disorders and in this case are seen on the stomach mucosa (blue). Due to Helicobacter pylori bacterial infection, a stomach (gastric) ulcer has formed here, with subsequent bleeding. Echinocytes are coloured pink. Magnification: x5560 at 6x7cm size."