Ulcerative colitis. Coloured scanning electron micrograph (SEM) of a freeze-fractured mucosal surface on the bowel of a patient suffering from ulcerative colitis. The surface (upper frame) has an irregular and disorganised structure, probably due to ulcerative colitis. The intestinal surface is covered with numerous microvilli and goblet cells (neither seen) that absorb nutrients and secrete digestive substances. The structure of the tissue below the surface is seen on the fracture plane in the lower frame. The three larger holes are empty blood vessels. Ulcerative colitis is the inflammation and ulceration of the colon and rectum. Magnification unknown.