Process of Digestion
1. Mouth: The mouth contains teeth, tongue, and salivary glands. Teeth break food into tiny pieces, saliva lubricates food and the tongue rolls food into a Bolus (food that has been chewed and mixed in the mouth with saliva) for swallowing. Ptyalin converts cooked starch into maltose.
2. Oesophagus: The muscular wall of the gullet contracts and relaxes so as to push food down slowly in a zig-zag manner. This process is called Peristalsis.
3. Stomach: The stomach is a large sac-like (a bag-like or pouched structure) organ. Food is churned and mixed with gastric juice which is then turned into a paste called Chyme. The wall of the stomach produces gastric juices which contain two Enzymes: Pepsin (which changes protein to polypeptides), rennin (which curdles milk), and Hydrochloric Acid (HCL) which acidifies the food and stops the action of saliva as well as killing germs which can enter your body in food.
4. Small intestine: this is a very long narrow tube made up of three parts namely: duodenum, jejunum, and ileum. In the duodenum, the pancreas produces pancreatic juice which contains three important enzymes:
i. Amylase (changes starch to maltose)
ii. Lipase (converts fats to fatty acid and glycerol)
iii. Trypsin (converts protein to polypeptides)
- The liver is also attached to the duodenum and produces a greenish liquid called BILE which emulsifies fats i.e reducing fats into smaller droplets. Bile is stored in the gall bladder. During the passage of food in the duodenum, the chime becomes watery and it is called Chyle.
- The walls of the ileum produce intestinal juices containing many enzymes that complete the process of digestion. The enzymes are sucrose, maltose, lactose, erepsin, and lipase.
5. Large intestine: Water is absorbed here.
6. Rectum: Faeces are retained here prior to egestion.
7. Anus: Its function is to control the expulsion of faeces