The need for digestion
The mammalian digestive system is based around a long tube called the alimentary canal. The alimentary canal stretches from the mouth to the anus.
Many of the foods we eat are too large and insoluble to be absorbed into the blood. These foods must be The breakdown of large insoluble food molecules to smaller soluble ones. to break them down into small soluble molecules that can be absorbed.
This breakdown is catalysed by specific enzymes. Food is digested in the mouth, stomach and small intestine and then absorbed into the blood through the lining of the small intestine.
Image caption, Protein digestion
1 of 3
Food absorption in the small intestine
The structure of the small intestine is specialised for rapid absorption of small soluble food molecules.
The lining of the small intestine is folded into millions of finger-like projections called Finger-like projections in the small intestine that provide a large surface area for the absorption of food.. This provides a very large surface area, which increases the speed of absorption of small soluble food molecules.
Each villus has the following specialisations to aid absorption:
- Its lining is only one cell thick, which increases speed of absorption.
- Capillaries in each villus to provide a good blood supply to take up and transport glucose and amino acids.
- A Central vessel in the villi responsible for the absorption of fats. to take up and transport the products of fat digestion.