An appendix is found only in humans a few species of great apes and the wombat about 6 cm long and 1cm in diameter it is a hollow organ that dangles from the cecum. The walls of the appendix are muscular and lined first with a layer of lymph tissue and then and innermost layer of epithelium. It is structurally similar to the colon and is also capable of peristalsis. The appendix has no known function we do not know why humans have one . since it vaguely resemble a lymph node the appendix may function to prevent intestinal infections .appendicitis or inflammation of the appendix is the most common cause of emergency surgery today. The appendix become a liability when its lumen becomes blocked by a  fecal material or by swelling of the lymph tissue in reaction to an infection . fluids secreted by the appendix then accumulate and become infected by intestinal bacteria the area then become inflamed swollen and painful. If not removed the appendix may burst and spread its infection through out the abdominal .Appendicitis symptoms are pain in stomach and other irritations.