The Body Digests Food, But Not Itself
by Jaleah Price, age 14
The digestive system is a process that involves many organs in the abdomen. The role of digestion is to convert food into useful material that provides the body energy, sustains growth, and repairs it when necessary. Digestion involves the mouth; esophagus; stomach; liver; gallbladder; pancreas; and the small and the large intestines.
Before food is digested, it must be chewed and swallowed in the mouth. Once the food is swallowed, it enters the esophagus, the tube that takes it to a stretchy, muscular bag called the stomach. This takes about 10 seconds. In the stomach, food is mixed with pepsin and hydrochloric acid and converted into thick liquid.
After food goes through the stomach, it is released into the small intestine where the bulk of digestion takes place. The small intestine is approximately 21 feet long. Food is pushed forward through the muscular walls of the esophagus, stomach, and small and large intestine in a forward motion; these contractions are called peristalses. In the small intestine, food combines with digestive juices from the liver, called bile. Bile breaks up fat and converts it into a soup like substance. Juices from the pancreas neutralize stomach acid and help digest carbohydrates, proteins, and fats.
The small intestine takes six hours to break down food properly and absorb nutrients in its inner lining. This small intestine lining is covered with villi. Villi are fingerlike projections that increase the small intestine surface area and absorb food. Nutrients dissolve into fluids that pass through the villi, where they enter blood vessels and are transported into the body.
Undigested food enters the large intestine, measuring in five feet, which absorbs water and minerals. After 12-36 hours in the large intestine, semisolid feces are collected in the rectum and ultimately released. Gut bacteria eat and produce the waste in the large intestine and give off vitamins useful to the body.
The digestive process takes over 18-30 hours on average to complete. Organs do not digest themselves because the lining of the stomach and intestines is covered with mucus. Mucus helps food slide through different digestive organs, while protecting it from acid and enzymes. The lining of the organs do wear away, but they often renew themselves by producing new cells. Therefore, since the organs produce new cells, they do not go through the process of digesting themselves.