How your food is digested
Find out about digestion of your food by viewing the diagram below for each part of your digestive system (salivary glands, oesophagus, stomach, pancreas, duodenum, jejunum and ileum, liver, gallbladder and large intestine).
1. Salivary glands
These secrete saliva, an alkaline fluid, to soften food, moisten the mouth and help swallowing. An enzyme called amylase starts to break down carbohydrate.
Food is pushed through the oesophagus by muscular contractions and relaxations.
The stomach is a holding tank. Special muscles enable it to move food around and break it down into smaller pieces.
The stomach lining secretes acidic gastric juices to digest carbohydrate and protein. Then the semi-digested food is delivered to the duodenum.
This produces enzymes which are secreted into the duodenum to digest protein, starch and fat.
Food can be digested here in only small amounts, so it's released from the stomach gradually when there is capacity to process it.
Pancreatic enzymes and bile finish off the chemical breakdown of the acidic stomach contents.
The inside surface is folded to increase the area for absorption of fats, sugars and amino acids.
5. Jejunum and ileum
Fats and other nutrients are absorbed here through the intestinal wall and are carried to the liver in the bloodstream.
The inside surface area of the jejunum and ileum is increased by folds and also by villi and microvilli (finger-like projections).
6. Liver and gallbladder
Incoming blood from the gastrointestinal tract brings glucose from food breakdown which is stored as glycogen.
Bile, which is involved in digestion and absorption of fats, is made in the liver.
The gallbladder, a small sac located on the under-surface of the liver, stores and concentrates bile. The consumption of fatty foods triggers the release of bile from the gallbladder into the intestine via a series of ducts.
7. Large intestine
The large intestine is made up of the caecum, ascending colon, transverse colon, descending colon and sigmoid colon and rectum.
Content from the small intestine comes in as fluid and gradually becomes solid as water and salts are absorbed out as it travels through the large intestine.
Mucus is secreted to aid the passage of faeces to the rectum.
- 1. Gastroenterological Society of Australia (GESA); Digestive Health Foundation (DHF). The digestive system; 3rd Edition, August 2010. http://www.gesa.org.au/consumer.asp?cid=23&id=210 (accessed Mar 2013).
2. National Digestive Diseases Information Clearinghouse (NDDIC). Your digestive system and how it works (updated 23 April 2012). http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/ (accessed Mar 2013.)