Organs responsible for digestion: The organs responsible for digestion of our food are teeth, gullet, oesophagus, stomach, small intestine, large intestine and pancreas.
Secretions for digestion: Three organs of our body, by their secretions,
Contribute to the digestion. They are (1) stomach secreting the gastric juice;
(2) Pancreas secreting the pancreatic juice, and (3) liver secreting the bile.
Alimentary canal: It is a very long coiled tube beginning from mouth and termineting at the anus. It consists of gullet, esophagus, stomach, small intestine, large intestine and rectum.
Small intestine: Food from the stomach enters the small intestine and mixes with bile and pancreatic juice coming from liver and pancreas. Bile has no digestive enzyme, so it does not take part directly in digestion. Pancreatic juice has three enzymes: trypsin, amylase and lipase.
Trypsin changes peptones and proteoses into polypeptides and amino-acids. Amylase turns starch and glycogen into maltose and lipase converts fat emulsions to fatty acids and glycerol. The digestion products are finally absorbed in the walls of small intestine and passes into blood.
Large intestine: This organ receives undigested materials of the food from the small intestine. It absorbs water and then passes the waste material into the rectum.
Liver: Bile is produced here which is stored in the gall bladder. Bile contains water, bile salts and bile pigments but has no digestive enzymes. It also contains salts like bicarbonate, glycocholate and taurocholate of sodium. Sodium bicarbonate neutralises the acid and makes the chummed food called chyme, alkaline; glycocholate and taurocholate of sodium break down the fats of tissues into small globules which mixes with water to form an emulsion.
Digestion Process: Teeth in our mouth break and chew up the food with the help of saliva coming from salivary glands, which converts starch into sugar. From the mouth the food goes to the stomach. The stomach makes gastric juice which kills harmful bacteria present in the food, and enzymes contribute in the digestion of proteins and fats.
Then the food becomes chyme and enters the duodenum where pancreatic juice from pancreas, bile from liver and intestinal juice from small intestine aid in digestion, absorption and excretion. The chyme now turns into chyle and is finally taken into blood. Undigested and unabsorbed products go out through the anus as faeces and urine through the bladder.