Ulcerative colitis. Coloured scanning electron micrograph (SEM) of a freeze-fractured section through the mucosa (lining) of the colon in a patient suffering from ulcerative colitis. This condition causes inflammation of the lining of the colon (large intestine) and rectum. The mucosa (dark pink) contains goblet cells (light pink, upper frame), which secrete lubricating mucus into the intestine. The numbers of goblet cells present may be reduced in this disease. The cause of ulcerative colitis is unknown, but its symptoms can be treated using anti-inflammatory drugs. Red blood cells (red) can be seen in the vascular tissue beneath the mucosa. Magnification unknown.