Digestion

Digestion is the process of breaking down food to absorb it. Food is broken down into smaller pieces, which are soluble in water. Only then can the food be absorbed into the bloodstream.

 Phases 
Digestion happens in three phases. 

Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces, which are made by digestive enzymes. In chemical digestion, enzymes break down food into the small molecules the body can use. Finally, the nutrients are absorbed into the blood stream. Once in the blood stream, the nutrients are taken to the liver, which is a kind of chemical factory for the body.

 Process 
After we swallow food, it travels down a muscular tube to the stomach. There, it is mashed into soupy fluid called chyme. The mixture passes into the small intestine, where tiny bits of food pass into the bloodstream. The food that is still left goes into the large intestine. Finally, waste products leave the body. 

Digestion usually takes about 18 hours. Food stays in the stomach for about three hours. Accessed 13 July 2010. If uncoiled, the small intestine would be about six meters (20 feet) long. Accessed 13 July 2010. Many digestive tracts are about as long as a bus.

Food slowly enters the small intestine from the stomach. This is where nutrients are taken into the blood. It then enters the large intestine. Water is taken away from it. The food that is left is called feces. The feces are stored in the rectum until the waste can leave the body through the anus.

Organs
Mouth
Tooth
Salivary gland
Parotid gland
Submandibular gland
Sublingual gland
Tongue
Palate
Hard palate
Soft palate
Uvula
Pharynx
Epiglottis
Oesophagus
Stomach
Small intestine
Duodenum
Jejunum
Ileum
Large intestine
Cecum
Colon
Rectum
Anus
Appendix
Liver
Biliary tract
Pancreas

 Related pages 
 nervous system

Other websites
 Human Physiology - Digestion 
NIH guide to digestive system 

 References 

Category:Digestive system
Category:Basic English 850 words