teachingscience

The Digestive System

An Overview

The digestive system is a group of organs that work like wrecking equipment to break down the chemical components of food, through the use of digestive juices, into tiny nutrients which can be absorbed to generate energy for the body. This system also builds and replaces cells and tissues, which are constantly dying. Digestion begins in the mouth with the teeth, which grind the food into small particles; the tongue, a powerful muscle which detects "good" and "bad" flavors in food and manipulates the food between the teeth for chewing, and saliva, a watery fluid which lubricates chewing and swallowing and begins the process of digestion. The digestive system begins in the mouth, continues in the pharynx (throat) and esophagus and into the "gut" region: the stomach, small and large intestines, the rectum and the anus. Food is chewed, pulped and mixed with saliva to become a soft mass which will easily travel down the esophagus. The tongue traps the food and forces it into the throat, which is a mass of muscles and tissues which transports food into the gut system for final processing and distribution. The throat closes the top of the breathing pipes, but if the food accidentally enters these pipes, it goes down the "wrong way" and must be coughed up before the body chokes or asphyxiates. As food passes through the body, it is mixed with an unbelievable amount of chemicals, which break it down into small units that can be absorbed into the blood and lymph systems. Some is used for energy, some as building blocks for tissues and cells, and some is stored for future or emergency use. The liver and the pancreas also secrete digestive juices that break down food as it passes through the digestive ducts. Not all that we eat can be digested, so the waste must be disposed of in an efficient way. It may not be a savory ending for the food or drink we thought was so delicious in the mouth, but it is just as important for our health.

GastroIntestinal System PowerPoint

http://www.umm.edu/digest/howworks.htm

http://library.thinkquest.org/15873/zoo/digestive/

http://www.acm.uiuc.edu/sigbio/project/digestive/index.html