Tuesday, May 10, 2011

Digestive System

Organs of the digestive system are specialized for the digestion and absorption of food. The primary function of the digestive system is to prepare food for cellular utilization. Food is broken down to be absorbed into intestinal wall and transported to the cells by the blood.

What is Gastrointestinal (GI) tract ?

The tube that extends from the mouth to the anus in which the movement of muscles and release of hormones and enzymes digest food.

GI Tract consist of :

- Ingest food
- Grinds food and mixes it with saliva

Pharynx (part of the throat)
- Receives bolus (mass of food that has been chewed at the point of swallowing)
- continues swallowing of bolus to oesophagus

Oesophagus (passage between the throat)
- Transport bolus to stomach

- Chums bolus with gastric juice
- initiate digestion of proteins
- sends digests food into duodenum (first section of the small intestine)

Small Intestine
- Receives chyme (partially digested food) from stomach
- Breakdown chyme
- Transport waste to large intestine

Large Intestine
- Receives undigested waste from small intestine
- absorbs water and electrolytes

Accessory organs of the GI tract

- Largest intestinal organ of the body approximately up to 3kg
- Produce bile to help breakdown of fats
- contains enzymes to breakdown many toxin or chemicals in food and drink

- Stores bile made by liver
- bile is release when food containing fat enters the liver

- Produce hormones including insulin and glucagons
- juice containing enzymes
- further breakdown carbohydrates, protein and fat in the chyme

Absorption and Transport of Nutrients

  • recommended approximately 60% of total calories come from carbohydrates
  • digestible carbohydrates are broken down by enzymes in the saliva, pancreatic juice and lining of small intestine
  • need to be digested before they can be used to build and repair body tissue
  • starts in the stomach and is completed in the small intestine
  • protein is broken down into amino acids
  • absorbed from the small intestine into blood and carried to all parts of body
  • rich source of energy
  • first step is to dissolve into content of intestine
  • bile acids produced by the liver assist in breakdown of large fat molecules in smaller which are fatty acids and cholesterol
  • bile acids, fatty acids and cholesterol combine to move into the mucosa (moist tissue layer of the stomach) of large intestine
  • the blood carries the remainders of the fat molecules for storage around the body


  • absorbed from the small intestine
  • classified by the fluid in which they can be dissolved
  • water soluble - vitamins B & C
  • fat soluble - vitamins A,D,E & K

Images & sources
Digestive system
Gastrointestinal track

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