The process by which the end products of digestion pass through the lining of the digestive tract is called absorption. Absorption takes place through the inner lining of the small intestine called villi. the simple sugar and amino acids enter into the blood directly while the fatty acids enter the blood system indirectly through the lymphatic system.
| Site | Digestive juice | Optimum pH | Enzyme | Functions (reactions) |
| Mouth | Saliva | Alkaline | Ptyalin | Starch maltose |
| Stomach | Gastric juice | Acidic (due to the presence of hydrochloric acid) | Pepsin Renin | Converts protein to peptide and peptone. Acts on milk proteins only and curdles it by converting the caseinogen (soluble) to casein (insoluble) |
| Duodenum | Bile secreted by the gall bladder Pancreatic juice produced by the pancreas | Alkaline Alkaline | Contains no enzyme but bile salts amylase Trypsin lipase | The bile salts emulsify the fats. Starch >>> maltose Protein >>> peptides/peptones Fats >>> fatty acids and glycerol |
| Small intestine or ileum | Intestinal juice | Alkaline | Maltase Lactase Sucrose Peptidase Lipase |
Assignment: draw and label fully a diagram showing the alimentary canal.
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