Ulcerative colitis. Coloured scanning electron micrograph (SEM) of goblet cells (green, round) on the mucosal surface of the bowels of a patient suffering from ulcerative colitis. The goblet cells secrete the mucus that lines the intestinal tract. The mucus is formed from mucigen granules (blue), seen in the goblet cells. The mucosal surface is covered with numerous microvilli (white) that absorb food nutrients and secrete digestive substances. Ulcerative colitis is the inflammation and ulceration of the colon and rectum. Magnification unknown.