2 - HUMAN NUTRITION 

Alimentary canal 

Mouth - 

- Salivary glands in the mouth produce amylase in saliva 

- Teeth break down food mechanically 

Oesophagus - 

- Muscular tube 

- Connects mouth and stomach 

Liver - 

- Produces bile 

Gall bladder - 

- Stores bile 

Stomach - 

- Pummels food with muscular walls 

- Produces pepsin (protease enzyme) 

- Produces HCl - kills bacteria, right pH for proteas enzyme (pH 2) 

Pancreas - 

- Produces protease, amylase, lipase 

- Releases enzymes into small intestine 

Small intestine -

- Produces protease, amylase, lipase 

- Nutrients absorbed into body 

- Contains villi 

Large intestine - 

- Excess water absorbed by blood 

Peristalsis - 

• Muscular tissue all the way down alimentary canal 
• Squeeze boluses through gut 
• Squeezing action - waves of circular muscle contractions 

Digestive process - 

1. Ingestion 

• Putting food in mouth 

2. Digestion 

• Break-down of large, insoluble molecules to small, soluble molecules 
• Mechanical - teeth and stomach muscles 
• Chemical - enzymes and bile 

3. Absorption 

• Process of moving molecules through the walls of the intestines into the blood 
• Digested food molecules absorbed in small intestine 
• Water mainly absorbed in large intestine 

4. Assimilation 

• Digested molecules have been absorbed, moved into body cells - become part of cells (assimilation) 
• eg: amino acids used by cells to make cellular proteins 

5. Egestion 

• Undigested materials form faeces 
• Egested 

Villi (small intestines) - 

• Small intestine - adapted for absorption of food 
• Very long - time to break down and absorb all food 
• Large surface area for absorption - covered in millions of villi 
• Each cell on surface of villi has microvilli - increase surface area further 
• Villi - single permeable layer of surface cells, very good blood supple for quick absorption