e . Nutrition

1. e. Nutrition We still need to learn: • Peristalsis • What bile is • Digestive enzymes • All about the microvilli

2. 2.31 Explain how the structure of a villus helps absorption of the products of digestion in the small intestine. • The small intestine is adapted for absorbing digested food very efficiently. • It is very long (about 7m in adults), which allows a long time for the food to be digested and absorbed as it moves through the gut. • The wall of the small intestine is covered in villi. • Each villi is covered with cells which have even smaller projections on them called, microvilli.

4. Microvilli • Microvilli give the inner surface of the small intestine a very large surface area. • This large surface area means that the food can be absorbed quicker. • Digested food is absorbed into the blood stream and then taken to the liver before it goes to the rest of the body. • These villi contain lots of blood vessels.

5. Villi • Villi have walls that are only one cell thick. • This allows the food to cross the wall easily and quickly to the blood capillaries. • Each villi is 1mm long. • The cells that cover the villi make enzymes. • These enzymes complete the digestion of food.

6. Villi contain lacteals. • Lacteals are part of the lymphatic system. • Fats are absorbed into the lacteals. • Villi also contain goblet cells. • Goblet cells make mucus.