What Is Mechanical and Chemical Digestion?

Mechanical digestion prepares food for chemical digestion in the body.
Mechanical digestion prepares food for chemical digestion in the body. (Image: Finger food - finger food pieces at Mediterranean wedding image by FotoWorx from Fotolia.com)

Mechanical digestion prepares food for chemical digestion, according to Hellolife.com. Protein and fats are significantly more difficult for the body to digest than carbohydrates. Complex enzymes are required to digest fats and proteins through chemical digestion, according to the National Digestive Diseases Information Clearinghouse. The process of chemical digestion is regulated by digestive hormones such as gastrin, secretin, Cholecystokinin, ghrelin and PeptideYY.


Mechanical digestion is the first step of the digestive process, according to Hellolife.com. Mechanical digestion first takes place in the mouth when food is chewed by our teeth. Mechanical digestion involves breaking food particles down into smaller particles. This makes it easier for digestive juices to break down food particles. Chemical digestion also begins in the mouth where simple sugars are broken down by saliva.


Food is processed in three ways--digestion, absorption and elimination--according to Hellolife.com. There are eight digestive enzymes that play a role in chemical digestion: nuclease, protease, collagenase, lipase, amylase, elastase, trypsin and chemotrpsin. Most digested molecules are absorbed through the small intestine, according to the National Digestive Diseases Information Clearinghouse.

Time Frame

The process of chemical and mechanical digestion takes between 24 and 72 hours, according to Hellolife.com. Food remains in the stomach for between six and eight hours where enzymes break food down and food is churned by stomach muscles through mechanical digestion.


After food leaves the mouth it travels through the esophagus to the stomach, according to Hellolife.com. Proteins are digested primarily in the stomach by digestive enzymes. Food moves from one organ to the next through peristalsis, when muscles squeeze food from one organ to another--a form of mechanical digestion. Food then enters the small intestine where most nutrients are absorbed. Food is then passed to the large intestine where the majority of water is absorbed and waste is stored. The large intestine is able to hold digested food waste for multiple days.


The human digestive track is approximately 30 feet long, according to Thinkquest.org. This is approximately five times the height of the average person.

Fun Facts

Approximately half a gallon of saliva is produced each day, according to Thinkquest.org. Human adult stomachs can hold slightly over half a gallon of material. Approximately eight gallons of food flow through the digestive system each day.

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