The digestive system helps to break down food and absorb accompanying nutrients into the body, according to the National Digestive Diseases Information Clearinghouse. The digestive tract consists of the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. Digestion, as reported by the Mayo Clinic, takes about 24 to 72 hours in the average healthy individual from the time you consume food to the time you excrete that food in urine or stool. During the stages of digestion, each digestive tract organ works to digest food through the help of certain enzymes, which chemically break down the food into particles that can be easily absorbed by body cells.
The Mouth
Chewing, also referred to as mastication, is the initial stage of digestion when food is broken down. At this stage of digestion, the enzyme salivary amylase, is released by the salivary glands and breaks down the carbohydrate particles in the food being consumed, according to an article in the "Advances of Physiology Education." The food also uses the saliva to form a bolus, or mass of food covered in water and mucous, which is more easily swallowed and transported through the esophagus, according to an article in the journal of "Oral Diseases." Once swallowed, the food is transported to the stomach through peristalsis, which according to the National Digestive Diseases Information Clearinghouse, is a wavelike motion of the ring-shaped muscles of the esophagus.
To the Stomach
Once the bolus of food reaches the end of the esophagus, the food passes through the lower esophageal sphincter and enters the stomach where, according to the National Digestive Diseases Clearinghouse, enzymes and digestive juices released from the stomach break down fat, protein, as well as carbohydrate into smaller particles. Once mixed and digested, food is transported from the stomach to the small intestine. The process of digestion through the stomach and small intestine, according to Mayo Clinic.com, takes about six to eight hours.
Intestinal Absorption
As food enters your small intestine, enzymes from various organs work together to break down the food into even smaller, more absorbable particles. Pancreatic amylase, released from the pancreas, works with other intestinal amylase enzymes, to break down carbohydrates into single compounds of carbohydrate known as monosaccharides, according to the National Digestive Diseases Information Clearinghouse. First, the panceatic amylase breaks down the starches and sugars into maltose, which is then broken down by intestinal enzymes into glucose, which is easily absorbed by the blood and can be utilized for energy. Protein is further digested in the small intestine by enzymes from pancreatic juices and the lining of the intestine, which break down the protein to amino acids. Amino acids are more easily absorbed through the small intestine into the blood where they are used to build cells and and other parts of the body. Finally, bile produced by the liver works to continue digestion of fats in food particles to smaller forms that can be absorbed by the pancreas and small intestine, which are then taken to various storage depots of the body. Once digestion is completed in the small intestine, food particles then enter the large intestine, or colon, for further digestion and absorption of water. It is in the colon, according to the Ohio State University Medical Center, where undigested food particles, such as fiber, are formed into waste products.
Elimination
Waste products, according to the Mayo Clinic, are eliminated through the large intestine usually starting after 24 hours. Complete elimination of waste products from the rectum and anus may take several days.
References
- National Digestive Disease Information Clearinghouse: Your digestive system and how it works
- Mayo Clinic: Digestion: How long does it take?
- "Advances in Physiology Education;" Insights into digestion and absorption of major nutrients in humans; Goodman, BE; 2010
- "Oral Disease;" Saliva and gastrointestinal functions of taste, mastication, swallowing and digestion; AM Pedersen, A Bardow, S Beier Jensen, B Nauntofte; 2002
- Ohio State University Medical Center: The Digestive System
