The Digestive System

The main purpose of the Digestive system is to break down food and absorb nutrients. There are two basic divisions to the digestive system, these are the gastrointestinal (GI) tract, also known as the alimentary canal, and the accesory digestive organs. Your mouth, pharynx, esophagus, stomach, small intestine and large intestine compose the GI tract, and your teeth, tongue, salivary glands, liver, gall bladder and pancreas are accessory organs.

The digestive system carries out six basic processes; ingestion, secretion, propulsion, digestion, absorption and defecation.

Ingestion is taking food into the mouth. Secretion is the act of expelling a liquid. The cells lining the GI tract secrete about 9 liters (9.5 quarts) of water, acid, buffers, and enzymes each day to lubricate the canal and aid in the process of digestion. Propulsion consists of alternating contraction and relaxation of smooth muscle in the walls of the GI tract to squeeze food downwards. Digestion has two parts, mechanical and chemical. Mechanical digestion is chewing up the food and your stomach and smooth intestine churning the food, while chemical digestion is the work the enzymes do when breaking large carbohydrate, lipid, protein and nucleic acid molecules down into their subcomponents -these and others are the nutrients-. Absorption occurs in the digestive system when the nutrients move from the gastrointestinal tract to the blood or lymph. Defecation is the process of expelling what the body couldn't use.

To see pictures and learn more about the organs of the digestive system, CLICK HERE.

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(images either taken from Gray's Anatomy Descriptive and Applied copyrighted 1946 or photographed by author, backgrounds courtesy of "The Wallpaper Machine" by Roy Williams and Bruce Sears)