Ulcerative colitis. Coloured scanning electron micrograph (SEM) of goblet cells (large, round) on the mucosal surface of the bowels of a patient suffering from ulcerative colitis. This surface is covered with numerous microvilli (not seen) that absorb food nutrients and secrete digestive substances. The goblet cells secrete the mucus that lines the intestinal tract. The mucus is formed from the mucigen granules (round) seen in the goblet cells. Ulcerative colitis is the inflammation and ulceration of the colon and rectum. Magnification unknown.