The digestive tract, also called the alimentary canal, consists of a group of hollow organs that provide a passageway for food and beverages. These organs function in the process of digestion, the breakdown of food particles to small molecules. The body absorbs these molecules into the bloodstream, distributes them to cells throughout the body and uses them for nourishment and energy. Digestion occurs due to the combined efforts of all the organs of the digestive system.
Mouth
As the first organ of the digestive tract, the mouth serves several vital functions. The mouth ingests the food and drink through the process of eating and drinking. Digestion also begins in the mouth through both mechanical digestion and chemical digestion. Mechanical digestion is the physical breakdown of food particles through mastication, or chewing, performed by the teeth and tongue. Chemical digestion utilizes enzymes in digestive juices, in this case in saliva secreted by salivary glands, to further breakdown particles into usable molecules.
Esophagus
As food is swallowed it enters the esophagus, a tube lined with layers of muscles. The University of Maryland Medical Center reports that the esophagus has one function---to transport food and liquids from the mouth to the stomach. The esophagus consists of layers of muscles which contract creating ocean-like waves that propel the food down toward the stomach, an action called peristalsis.
Stomach
The stomach performs three main tasks, according to the National Digestive Diseases Information Clearinghouse. First, it serves to store swallowed food and liquids. Second, the lining of the stomach secretes digestive juices and acid which mix with the food and liquid aiding in digestion. Third, the muscles of the stomach work to empty the contents into the small intestine.
Small Intestine
The small intestine performs several major digestive functions. The lining of the small intestine consists of finger-like projections known as villi. These villi increase the surface area of the small intestine wall which increases the molecules absorbed. The small intestine absorbs 90 percent of the nutrients from the digested food, according to the Internet Encyclopedia of Science. The small intestine functions in digestion as the digestive juices secreted by the pancreas enter the duodenum, the upper portion of the small intestine. The wall of the small intestine consists of muscles which continue the peristalsis movement propelling contents on toward the large intestine. Other functions of the small intestine unrelated to digestions include hormone secretion and protection against infections.
Large Intestine
The large intestine processes waste. It receives particles remaining after digestion, usually in liquid form. As the waste moves through the large intestine, also called the colon, water is removed aiding in the process of elimination.
Rectum
The rectum is approximately an 8-inch chamber which connects the large intestine to the anus, according to the Cleveland Clinic. The rectum functions to receive stool from the colon, triggering the feelings of needing to defecate and then holding the stool until evacuation.
Anus
The anus, the final organ of the digestive system, detects contents in the rectum, determines if it is solid, gas or liquid and controls the release of stool.
References
- University of Maryland Medical Center: Normal Function of the Esophagus
- Internet Encyclopedia of Science: Small Intestine
- Cleveland Clinic: Structure and Function of the Digestive System
- National Digestive Diseases Information Clearinghouse: Your Digestive System
- Internet Encyclopedia of Science: Mouth
