What Is Chemical Digestion?

The foods you eat must be broken down into their smallest components.
Image Credit: Jacob Wackerhausen/iStock/Getty Images

No matter how nutritious, your favorite foods won't do you any good in their natural, whole state. The nutrients your body gets from food must be small enough to absorb easily into your bloodstream. Through the use of specialized chemicals, your body's digestive process continuously breaks food down into smaller and smaller pieces until its vitamins, minerals, amino acids and fatty acids are "unlocked" and able to perform their jobs.



Your body utilizes two types of digestion: chemical digestion and mechanical digestion. Chemical digestion refers the to the breakdown of food in the mouth, stomach and intestines through the use of acids and enzymes. Mechanical digestion processes--such as chewing, swallowing and the muscular movements that move food through the digestive tract--support chemical digestion by physically breaking whole foods into smaller pieces to facilitate chemical breakdown.


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How Chemical Digestion Begins

Chemical digestion doesn't begin in your stomach, but in your mouth. The moment you see, smell or even think about food, your mouth begins to produce extra saliva. Saliva contains an amylase enzyme called ptyalin, which breaks starches down into dextrose and maltose by adding a water molecule into the starch compound. Once food is swallowed, powerful muscles in the esophagus push it downward into the stomach in a continuous wave motion.


Stomach Function

According to JRank Science Encyclopedia, while your food is still in your mouth, glands in your cheeks and tongue send signals to your brain, which prompt glands in your stomach lining to begin secreting gastric juice. Once the food hits your stomach, more gastric juice is produced. Your stomach mixes the juice in with the food as it churns, dissolving it into a thick, creamy liquid called chyme. Little by little, chyme is deposited into the small intestine.


Gastric Juice Composition

Gastric juice comprises a specialized enzyme that breaks down proteins, called pepsin, and hydrochloric acid. According to the U.S. Division of Education's Newton BBS Ask a Scientist website, the hydrochloric acid in your stomach has a pH of 1 to 2, which makes it about one million times more acidic than water. It is powerful enough to dissolve most foods, and many of your body's tissues as well. Your stomach has a thick mucous lining that protects it from its own acid. A sphincter placed where your esophagus meets your stomach prevents the acid from leaking out and damaging your upper digestive tract.


Intestinal Function

According to the National Digestive Diseases Information Clearinghouse, chyme deposited into the small intestine mixes with enzymes, bile and fluids secreted by the intestinal walls. The enzymes, which are produced by the pancreas, break down carbohydrates, proteins and fats. The liver produces bile, which dissolves fats in much the same way dish detergent dissolves grease. By the time chyme reaches the large intestine, it has been broken down into its smallest possible components. These pass through projections on the intestinal wall, called villi, and into the bloodstream, where they are distributed as needed. Undigested material, such as water, fiber and cellulose, is excreted from the body.




Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.

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