3.3
Human Digestive System
| 3.3 |
Human Digestive System |
- Food digestion is a process of breaking down food that is complex into small molecules and soluble so that they can absorbed by the body cells
| Digestion |
| Physical |
| The process of breaking down food into smaller particles with the help of teeth,tounge and saliva. Involves peristalsis |
| Happens in the mouth |
| Does not involve enzymes |
| Chemical |
| The process of breaking down food from complex molecules into simple molecules with the help of enzyme |
| Happens in the mouth,stomach,duodenum and intestine |
| Involves enzymes |
| The Structure of the Human Digestive System |
1)Mouth
- Food is chewed by teeth.
- Salivary amylase in saliva breaks down starch into maltose.
2) Oesophagus
- Food that enters oesophagus is called bolus.
- The process of peristalsis pushes the food into the stomach.
3)Stomach
- Wall of stomach secrete protease and hydrochloric acid.
- Hydrochloric acid activates protease which breaks down protein into polypeptides. Semi-liquid food is called chyme.
4) Duodenum
- Liver produces bile which emulsifies fat into small droplets and neutralises the acid in the chyme.
- Pancreas produces pancrestic juice which contain enzymes amylase,protease and lipase.
- Pancreatic amylase digests starch into maltose
- Protease digests polypeptides into dipeptides
- Lipase digests fat into fatty acids and glycerol
5) Small intestine
- Maltase digests maltose into glucose
- Protease digests dipeptides into amino acids
6) Large intestine
- Undigested food enters large intestine
- The process of water reabsorption happens
7) Rectum
- Food that is undigested, known as faeces, enters the rectum and is stored here
8) Anus
- Faeces are excreted from the body through the anus
