The digestive system has three main functions: digestion of food, absorption of nutrients, and elimination of solid waste.
In the digestive process we can consider four stages:
Stage 1: Ingestion.
The intake of food into the body trhough the mouth
Stage 2: Digestion .
The transformation of food into nutrients which the body can absorb. There are two types of digestion:
Mechanical digestion is the physical breakdown of chunks of food into smaller pieces. It takes place mainly in the mouth and stomach.
Chemical digestion: is the chemical breakdown of large, complex food molecules into smaller, simpler nutrient molecules that can be absorbed by the blood. It takes place mainly in the small intestine and trhough the action of enzymes.
Enzymes are substances that speed up chemical reactions. Digestive enzymes speed up the reactions of chemical digestion. Digestive enzymes are secreted by glands in the mucous membranes of salivary glands, stomach, small intestine, and pancreas.
The name of a digestive enzyme typically ends with the suffix -ase, which means “enzyme”. The rest of the name refers to the type of food molecules the enzyme helps digest. For example
proteases split proteins into their monomers, the amino acids
lipases split fat into three fatty acids and a glycerol molecule.
amylases split starch into sugars.
In this video you can learn a little more about enzymes It’s in english but you have in the same page the transcrip of the video.
Stage 3: Absorption:
Absorption is the process in which nutrients pass from the digestive system into the blood stream, where they can circulate throughout the body and carry the nutrients to the cells. Absorption occurs mainly in the small intestine
Stage 4: Egestion:
Egestion is the elimination of undigested food that cannot be absorbed and waste products from the digestive system. These products are transformed into faeces, and expelled from the organism through the anus.
It should not be confused with excretion, which is getting rid of waste formed from the chemical reaction of the body, such as in urine, sweat, etc.