Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
Related to self-digestion: heterolysis


(sĕlf′dĭ-jĕs′chən, -dī-)
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


[L. digestio, a taking apart]
The process by which food is broken down mechanically and chemically in the gastrointestinal tract and converted into absorbable forms. Salts (minerals), water, and monosaccharides can be absorbed unchanged, but starches, fats, and proteins must be broken down into smaller molecules. This is brought about by enzymes, each of which acts on a specific type of food and requires a specific pH to be effective. See: table

Hormones released by the gastrointestinal mucosa stimulate the secretion of digestive enzymes and bile and influence the motility (peristalsis) of the stomach and intestines. Starches and disaccharides are digested to monosaccharides; fats are digested to fatty acids and glycerol; proteins are digested to amino acids. During digestion vitamins and minerals are liberated from these large organic molecules. See: intestinal hormone

artificial digestion

Digestion occurring outside the living organism by an enzyme.

chemical digestion

The conversion of complex food molecules into simpler molecules by digestive enzymes.
See: table

duodenal digestion

That part of digestion that occurs in the duodenum where stomach contents mix with biliary and pancreatic secretions. The duodenum absorbs iron, vitamin B12, and other essential nutrients.
See: duodenum

extracellular digestion

Digestion outside a cell, as of tissue by bacterial enzymes (toxins).

gastric digestion

That part of digestion that takes place in the stomach.
See: stomach

intestinal digestion

That part of digestion that occurs in the intestine.
See: absorption; large intestine; small intestine

intracellular digestion

The consumption and chemical degradation of materials ingested by cells (e.g., bacteria, viruses, or large molecules) within vacuoles in the cytoplasm.

lipolytic digestion

The conversion of neutral fats by hydrolysis into fatty acids and glycerol; fat splitting.

mechanical digestion

The conversion of food into small pieces by chewing, churning of the stomach, or the emulsifying action of bile salts, exposing more surface area to digestive enzymes.

oral digestion

That part of digestion that takes place in the mouth. It includes the physical process of chewing food and the chemical process of starch splitting by the enzyme amylase, present in the saliva.

pancreatic digestion

The digestion of proteins and fats by pancreatic enzymes released into the intestine.

parenteral digestion

The digestion of foreign substances by body cells as opposed to enteral digestion, which occurs in the alimentary canal.

salivary digestion

Digestion of starches by salivary amylase.


Food ComponentEnzymeSecretionSite of Action
ProteinsPepsinGastric juice, acidStomach
TrypsinPancreatic juice, alkalineSmall intestine
PeptidasesIntestinal juiceSmall intestine
FatsLipaseGastric juiceStomach
Pancreatic juiceSmall intestine
CarbohydratesSalivary amylaseSaliva, alkalineMouth
Pancreatic amylasePancreatic juiceSmall intestine
Sucrase, maltase, lactaseIntestinal juiceSmall intestine
Medical Dictionary, © 2009 Farlex and Partners
Full browser ?