Digestion is the process by which your body breaks down food into small nutrient molecules. Digestion can be mechanical or chemical. In mechanical digestion, bites of food are torn or ground into smaller pieces. Chemical digestion breaks foods into their building blocks. Chemical digestion takes place in many parts of the digestive system.
Absorption occurs after digestion. Absorption is the process by which nutrient molecules pass from your digestive system into your blood. Most absorption occurs in the small intestine.
Food material that is not absorbed is eliminated (removed) after passing through the large intestine.
Digestion begins in the mouth. Both mechanical and chemical digestion occurs in the mouth. Your teeth and tongue tear apart and grind food into smaller pieces – Mechanical Digestion The saliva in your mouth contains enzymes that break apart carbohydrates (sugars).
Enzymes are proteins that speed up chemical reactions in the body. They have a specific shape and only work with chemicals that fit their specific shape!
After chewing and thoroughly covering your food in saliva, you swallow the mass of food and it heads down your esophagus. Food is pushed through the esophagus (and the remainder of your digestive system) by smooth muscle movements called peristalsis. The muscles behind the food contract and keep pushing the food forward through the digestive system.
Mechanical and chemical digestion takes place in the stomach. The stomach grinds and contracts around food while exposing it to very strong acids which break the food down into a mostly liquid substance called Chyme. Once the food has been properly liquefied, peristalsis pushes the food out of the stomach and into the small intestine.
When the chyme first enters the small intestine, it is exposed to many enzymes and a chemical from the liver called bile. These chemicals further break down the food particles. The smallest food particles are absorbed through the small intestine and are put into the bloodstream. Anything that remains is passed onto the large intestine
The large intestine does not absorb many nutrients, most of that is done in the small intestine. However, the large intestine does absorb a lot of water, drying out the food mass before it is eliminated from the rectum.
The nervous system receives input from the digestive system to make you feel hungry, full, or thirsty. The musculoskeletal system is responsible for peristalsis, which keeps food moving through your digestive system. Nutrients from what you eat are directly put into the circulatory system through the small intestine.