About the Human Digestive System
The digestion system is how the body consumes food, absorbs it in the intestines, and secretes the waste products. The digestive system runs from the mouth, through the stomach, into the small intestines where food is broken down and absorbed, and then excreted through the colon and anus. The digestive system is how the body gets energy for metabolism and activity. Knowing its function helps a person understand how the body metabolizes food after it's consumed.
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Esophagus
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The esophagus is the pipe that connects the mouth to the stomach. The esophagus is lined with smooth muscle, which forces the food down the pipe to the stomach. The end of the esophagus has a valve that opens and closes when food enters the stomach. People who suffer from GERD (gastroesophageal reflux disease) have valves that do not close tightly, so stomach acid is able to enter the esophagus, causing pain and tissue damage.
Stomach
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The stomach has a very low pH due to its acid content. When food is swallowed, the stomach produces hydrochloric acid. This acid has a pH of 2, making it a very strong acid. Food settles in the stomach where acid causes it to begin break down. The amount of time food sits in the stomach is dependent on the type of macromolecule. For instance, carbohydrates spend the least amount of time in the stomach.
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Small Intestine
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The stomach slowly empties its contents into the small intestine. The small intestine is where most nutrients are absorbed. The pancreas produces the enzymes that break down food into smaller molecules where they can be absorbed by the small intestine. The digestive enzymes from the pancreas play a large role in absorption. Each type of macromolecule is broken down by a different enzyme from the pancreas.
Pancreas
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The pancreas excretes the enzymes necessary for food absorption. There are three enzymes excreted from the pancreas: lipase, protease, and amylase. The names of these enzymes are associated with the foods they break down. Lipase catalyzes lipid break down. Protease is for proteins, and amylase breaks down sugars.
Colon
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Once food is absorbed, the contents that are not used are sent to the colon. The large intestines are the location for high volumes of water absorption as well. The colon is not as long as the small intestines, but it is larger in diameter, which is why it's referred as the large intestine. The colon is connect to the anus, where waste product is excreted, completing the digestive process.
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