Stages of digestion

• Ingestion - large food particles are taken into the mouth and broken down by the action of teeth, saliva and the tongue (mastication) so it may move into the gut.
• Digestion - breakdown of large food molecules to small, soluble molecules. Either mechanical breakdown by the action of teeth, saliva and tongue (mastication) or chemical breakdown by enzymes
• Absorption - small, soluble food molecules move from the small intestine, through the gut wall into the blood stream, which transports them to cells
• Egestion - undigested food exits the body as faeces, via the colon, rectum and anus
• Chemical digestion - the chemical breakdown (by enzymes) of large food molecules into small, soluble molecules
• Assimilation - transport and uptake of the dissolved soluble nutrients to the body cells
• Mechanical digestion - breaking up large food pieces into smaller food pieces. This increases the surface area of food over which enzymes act to chemically digest food.
• Stages of digestion:

  1. Ingestion
  2. Digestion
  3. Absorption
  4. Assimilation
  5. Egestion