NGR 5141 - Module 5 Questions and Answers () (Verified Answers).

1. Analyze why ulcerative colitis is hypothesized to be caused by genetic or immune factors rather than infectious agents. Although the exact cause of ulcerative colitis has not been determined, genetic and immune factors are thought to play a role. Inflammation can be caused by commensal or pathogenic enteric microorganisms that have increased mucosal adherence and invasion in addition to the continued activation of T cells. Because of the occurrence of ulcerative colitis in identical twins, it is thought to have a genetic basis. Humoral and cellular immunologic factors have been associated with ulcerative colitis. IgG antibodies and a large number of plasma cells have been found in individuals with ulcerative colitis. The T cells found in those affected may have cytotoxic effects on the epithelial cells of the colon and damage caused by inflammatory cytokines, toxic oxygen radicals, and interferongamma. Macrophages become activated and release cytokines which cause fever and the acute response. Autoimmune disorders, like lupus, can also accompany ulcerative colitis. 2. Discuss the pathophysiologic relationship between cirrhosis and portal hypertension. Portal hypertension is caused by a disorder that obstructs or impedes blood flow through the component of the portal venous system or vena cava. The excess pressure in these portal veins causes vessels to open between the portal and systemic veins. Blood is then able to bypass the obstructed portal vessels. The collateral veins evolve in the esophagus, anterior abdominal wall, and rectum. The high pressure and heightened flow volume are carried through these veins from the portal to the systemic venous circulation. Cirrhosis is irreversible and develops over many years. Structural changes in the liver are a result of fibrosis which is a consequence of leukocyte release, inflammatory cytokines, and chemokines with activation of fibrogenic fibroblasts. Obstruction caused by cirrhosis can cause portal hypertension. New vascular changes can form shunts and blood from the portal vein can avoid the liver. These vascular changes then cause liver function to be further decreased and regeneration is replaced by hypoxia, necrosis, atrophy, and finally complete liver failure. 3. Why does dumping syndrome occur following some gastric surgery? Dumping syndrome that occurs after gastric surgery is because of changes in motor and control functions of the stomach and upper small intestine. Early dumping syndrome can be caused by a loss of gastric capacity, a loss of emptying control and the pylorus is removed, and a loss of feedback control by the duodenum when it is removed. The rapid gastric emptying and creation of high osmotic gradient in the small intestine causes a sudden shift of fluid from the vascular compartment to the intestinal lumen. Dumping syndrome is