4.8 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine

After food passes through the duodenum, it enters the small intestine where it is
absorbed into the blood stream. The small intestine is highly adapted to absorb the 
digested food in many ways. 

Villus
The surface of the small intestine is lined with millions of villi. 

Adaptations of the small intestine:
1. Very long: gives plenty of time for digestion and for food to be digested
2. Has a lot of villi: villi gives the small intestine a larger surface area, the larger the surface area, the faster food can be absorbed
3. Villi contain blood capillaries: digested food passes into the blood to be taken to the liver and the rest of the body, small diffusion distance
4. The walls of the villi are only one cell thick: allowing digested food to pass through the walls easily to enter the blood capillaries