<P> Inflammatory bowel disease affects the layers of the gastrointestinal tract in different ways . Ulcerative colitis involves the colonic mucosa . Crohn's disease may produce inflammation in all layers in any part of the gastrointestinal tract and so can result in transmural fistulae . </P> <P> A perforated ulcer is one that has eroded through the layers of the gastrointestinal tract . </P> <P> Invasion of tumours through the layers of the gastrointestinal wall is used in staging of tumour spread . This is associated with prognosis . </P> <P> The normal thickness of the small intestinal wall is 3 - 5 mm, and 1 - 5 mm in the large intestine . Focal, irregular and asymmetrical gastrointestinal wall thickening suggests a malignancy . Segmental or diffuse gastrointestinal wall thickening is most often due to ischemic, inflammatory or infectious disease . </P>

Among the gi organs which has the strongest muscles