The large intestine is found at the end of the digestive tract. It is here where the final effort is made to extract nutrients from the passing food, and where faeces is formed. The large intestine also is responsible for reabsorption of water to maintain the appropriate fluid balance throughout the body. The large intestine reaches a length of about 1.5 meters.
The first section of the large intestine is the caecum. It is a small pouch shaped bulge in your lower right abdomen This is where the small intestine meets the large intestine. Taking partially digested food from the small intestine through the ileocecal valve separating the small and large intestines, the caecum begins passing the food toward the colon. At this stage the food typically contains fibre and other undigested food, water, undigested vitamins and minerals. Protruding out from the caecum is the appendix. The colon has four distinct sections: the ascending colon, the transverse colon, the descending colon and the sigmoid colon. The ascending colon begins at the caecum and rises up the abdomen on your right side. The transverse colon lays across the abdomen, just below the belly button. The descending colon then drops along the left side of the abdomen and meets with the sigmoid colon, the “S” shaped section between the descending colon and the rectum.
Just as in the esophagus and small intestine, the contents of the large intestine move along by the muscular prodding called peristalsis.
Faeces forms from a mixture of undigested food, fibre, mucus and bacteria. Faeces is passed from the sigmoid colon through the internal sphincter and into the rectum where it collects before release via bowel movement through the external sphincter.
While most of the nutrients from food are absorbed in the small intestine, the large intestine also absorbs it’s share of nutrients, mostly water sodium, chloride and potassium. Digestion in the large intestine is aided by intestinal bacteria. These bacteria also are responsible for the production of vitamin K. Vitamin K is required for the proper functioning of proteins involved in blood clotting. While vitamin K can be found in some foods such as leafy greens and cauliflower, production of vitamin K by bacteria in the large intestine is the body’s primary source. So it is important to keep a healthy intestinal flora.
References:
http://www.gesa.org.au/digestive-system/large_intestine.cfm
http://health.howstuffworks com/digestivesystem2.htm
http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/vitamink.html
Nutrition By Paul M. Insel, R. Elaine Turner, Don Ross
