How Does Digestion Work?
While no one spends much time thinking about the process of digestion, it is truly an amazing thing. Somehow the body sorts through all that a person eats, separates and absorbs all the nutrients from that food, and eliminates what it does not want or need. Digestion is one of the most truly unappreciated processes in the body, but without it people could not survive.
The Digestive System
Swallowed food first moves into the esophagus. It is the connection between the throat and the stomach. Between the esophagus and the stomach is a valve that stays closed until food moves through the esophagus. This valve opens to allow food to pass into the stomach. The stomach performs its functions on the food, and from the stomach the food goes into the small intestines. What food is not absorbed through the walls of the intestines travels into the colon. (The colon is part of the large intestine.) The food products left then stay in the colon for one or two days until leaving the body through the rectum and anus in a bowel movement.
The Movement of Food
The hollow organs that make up the digestive system have their own muscles and nerves that make their walls move in a wave-like motion called peristalsis. The first dynamo in this process is the act of swallowing the food. It sets off a chain reaction of involuntary processes that keep the walls of the organs-with the nerves of the digestive system-pushing the food forward.
The Digestive Process
Once the food passes through the valve between the esophagus and the stomach, the stomach performs three key functions. The stomach first stores the food. Then the lower part of the stomach mixes it up along with its own digestive juices. When this process is completed, the stomach then empties into the small intestine. The pancreas and liver get involved here to help the small intestine. Here the food is digested and absorbed through the walls of the intestines. Anything undigested at this point is considered a waste product and is passed into the colon and later pushed out of the body.
The Digestive Juices
The first set of digestive juices is found in the mouth, and they are the salivary glands. The saliva contains an enzyme that helps break down starch into smaller particles. The stomach also contains digestive glands. They make stomach acid and an enzyme that helps digest protein. Once the food is in the small intestine, the pancreas, liver and gallbladder begin to work. The pancreas makes enzymes to dissolve protein, carbohydrates and fats. The liver produces bile which is stored in the gallbladder. Bile dissolves fats in the intestines. Again, what is left is a by-product and will leave the body.
One puzzling thing that occurs is that the stomach acid that breaks down so much food does not burn holes through the stomach or even the lining of the stomach. There are so many things that have to occur to nourish the body in the digestive process, and it does so again and again and again. Digestion is an amazing feat.
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