Human colon is devided into three sections, ascendence, transcendence, and descendence. The colon tract ends in an area which is so-called rectum. Rectum has muscle that plays a role to hold the feces not to go into anus the anus, know as Huston valve.
The structure of secum as a conjoint of small intestine and large intestine
Large Intestine (Colon ) and Anus
Large intestine and small intestine are separated by a valve called ileosecum which is necessary to prevent food from coming bact into small intestine. At the end of ileosecum, there is appendix and cecum. Colon reabsorbs water and mineral that come from material waste of small intestine.
Large intestine contains a population of symbion bacteria that function in the substrate of plant cellulose, pectin, removed intestinal cells, and polysaccharide from intestinal mucosa. The fermentation results are organic acid, metan gas, and hydrogen. During digestion, there are also bacteria population producing vitamin B and K. The vitamin is absorbed by the cell of large intestinal surface. The waste material of digestive process is thrown away through anus (defecation).
In herbivore, appendix is a useful organ. In appendix, microbes break down plant cellulose. For human, the appendix is only a dead end vessel. Sometimes, food particles are lost in there. The appendix, then, will inflame and has to be cut off.
Source Biology, 2004.