Definition of physical digestion and chemical digestion

Physical digestion, also known as mechanical digestion, refers to the digestion process in which food is chewed by the mouth, ground by the teeth, stirred and swallowed by the tongue, and moved by the gastrointestinal muscles, so that large pieces of food are broken into small pieces, the digestive juice is fully mixed with the food, and the lump or chyme is pushed down from the mouth to the anus.

chemical digestion refers to the chemical decomposition of food by digestive juice secreted by digestive gland, and various digestive enzymes secreted by digestive gland decompose complex nutrients into simple compounds that can be absorbed by intestinal wall, such as sugars into monosaccharides, protein into amino acids, and lipids into glycerol and fatty acids.

Extended information:

First, the basic functions of the digestive system

The basic physiological functions of the digestive system are to ingest, transport and digest food, absorb nutrients and excrete wastes, and the completion of these physiology is conducive to the coordinated physiological activities of the whole gastrointestinal tract.

The digestion and absorption of food provide the substances and energy needed by the body. Except for vitamins, water and inorganic salts, the nutrients in food can be directly absorbed and utilized, but protein, fat and sugar cannot be directly absorbed and utilized by the body, and can only be absorbed and utilized by being decomposed into small molecular substances with simple structure in the digestive tube.

The process that food is broken down into small molecules with simple structure and can be absorbed in the digestive tube is called digestion. The process of this small molecular substance entering the blood and lymph through the mucosal epithelial cells of digestive tract is absorption. For the unabsorbed residue, the digestive tract is excreted in the form of feces through the large intestine.

the digestion process includes two functions: physical (mechanical) digestion and chemical digestion. As far as chemical decomposition of food is concerned, various digestive juices secreted by digestive glands decompose complex nutrients into simple compounds that can be absorbed by intestinal wall, such as sugars into monosaccharides, protein into amino acids, and lipids into glycerol and fatty acids.

Then these decomposed nutrients are absorbed by the small intestine (mainly jejunum) and enter the body, blood and lymph. This digestion process is called chemical digestion.

Mechanical digestion and chemical digestion are carried out at the same time, and * * * completes the digestion process.

second, digestion regulation

in the process of digestion, the activities of various parts of the digestive system are closely related and coordinated with each other. For example, when the movement of digestive tube is enhanced, the secretion of digestive juice is also increased, so that digestion and absorption can be carried out normally.

Another example is that when food is chewed in the mouth, it reflexively causes the movement and secretion of the stomach and small intestine to be strengthened, so as to prepare for accepting and digesting food. The coordination of various parts of the digestive system is realized through the regulation of nerve and body fluid under the control of the central nervous system.

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