Digestion

Digestion is the process whereby a biological species processes food to produce usable nutrients. Digestion usually involves mechanical manipulation and chemical action. In most vertebrates, digestion is a multi-stage process in the digestive system, following ingestion[?] of the raw materials, most often other organisms. The process of ingestion usually involves some type of mechanical manipulation.

In humans:

• Digestion begins in the mouth where the food is masticated with the teeth, thereby releasing enzymes from saliva into the food, and starting a reaction with the enzymes in the food itself.
• The food is then further compressed by being sent through the oesophagus to the stomach, a large pouch, where it is churned and thoroughly mixed with acid to chemically decompose it.
• As the acidic level(ph) changes in the stomach and later parts of the digestive tract, specific enzymes are activated or deactivated to extract and process various nutrients.
• Then passed into the small intestine where it is further mixed with secretions such as liver bile, to help digest fats, and pancreas insulin, to process sugars; Most nutrient absorption takes place in the small intestine.
• The final stage in human digestion is the movement of the matter into the large intestine, where water is re-absorbed before defecation.

Not only animals digest food. Some carnivorous plants capture other organisms, usually invertebrate animals, and chemically digest them. Fungi also are very effective at digesting organic material.