What Are the Four Main Functions of the Digestive System?

Reviewed on 2/1/2021

What Is the Digestive System?

Motility, digestion, absorption and secretion are the four vital functions of the digestive system.
Motility, digestion, absorption and secretion are the four vital functions of the digestive system.

The digestive system breaks down the foods we eat into energy our bodies can use. 

The organs that make up the digestive tract include: 

Bacteria in the gastrointestinal tract (also called gut flora or microbiome) also help with digestion, along with parts of the nervous and circulatory systems.

What Are the Four Main Functions of the Digestive System?

The main functions of the digestive system include: 

  • Motility
    • Food moves through the digestive tract due to a process called peristalsis, which is the movement of muscles in the GI tract that move the food through the digestive system 
    • This involves the breakdown and mixing of ingested nutrients all the way through the elimination of undigested waste from the body
  • Secretion
    • This is the release of enzymes, hormones, and other substances that help the body digest the food that is eaten
    • Hormones tell the body when to produce digestive juices and signal the brain when you are hungry or full
  • Digestion
    • Ingested nutrients including proteins, fats, carbohydrates, vitamins, minerals, and water are reduced into molecules small enough to pass through the lining of the gut and so they can enter the bloodstream 
    • The digestive system breaks down foods we consume so the body can use them for energy, growth, and cell repair
      • Proteins break down to amino acids
      • Fats break down to fatty acids and glycerol
      • Carbohydrates break down to simple sugars
  • Absorption
    • The digested nutrients pass from the gut into the blood so the circulatory system or lymph system can pass them on to the rest of the body to use or store 
    • The lymph system absorbs fatty acids and vitamins
    • The blood carries simple sugars, amino acids, glycerol, and some vitamins and salts to the liver
      • The liver stores, processes, and delivers these nutrients to the body when needed

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Reviewed on 2/1/2021
References
https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works

http://www.s-hamilton.us/BiologyHomepage/Term4-98/keittreim-digestivesystem/tothe.htm