How the digestive system works; 2 MINUTES ON.
Byline: DR MIRIAM STOPPARD
Once food is in your mouth, salivary glands produce saliva to lubricate it and break it down. You have three major pairs of larger salivary glands -- the parotid, sublingual and submandibular glands - which together produce about two pints of saliva a day, the secretion which contains an enzyme which starts digestion of carbohydrates.
Your teeth break down food while your tongue mixes it with saliva. As you swallow, the muscles in your mouth and throat push the food into your upper oesophagus (gullet), the tube that connects your throat to your stomach.
Muscles in the wall of your oesophagus push the food down toward your stomach. When it reaches the lower end, pressure from the food signals a valve, the lower oesophageal sphincter, to relax and let the food enter your stomach.
The digestive glands in your stomach lining produce acid and enzymes which mix with the food creating a paste called chyme. Once mixed, chyme is pushed through a valve into the first section of the small intestine (duodenum), about 4ml at a time. Here, chyme mixes with digestive juices from your pancreas, liver and gallbladder to digest protein and fats.
Bile and pancreatic digestive juices mix with more enzymes secreted by the wall of your small intestine. Further down in the jejunum, it's broken down into smaller molecules of nutrients that can be absorbed into the bloodstream.
What remains is water, minerals such as sodium and chloride, and waste products, such as indigestible fibre. In the colon nearly all the water is absorbed. Muscles in the wall of your colon separate the waste into small segments and when the sphincter muscles in your anus relax, the rectal walls contract to increase pressure and expel the stool.