The small intestine is adapted for efficient food absorption in several ways: (1) it has a highly folded inner wall with many villi that provide a large surface area for absorption, allowing enough time for nutrients to be absorbed; (2) long villi shorten the distance for absorption; (3) the thin wall of the villi contains a network of blood capillaries that quickly carry away absorbed food molecules to the rest of the body.

3. Longitudinal section of villi

7. m onosaccharides e.g. glucose amino acids water-soluble vitamins Absorption of digested food i) i nto the blood minerals

8. all parts of the body Absorption of digested food i) i nto the blood liver

10. Absorption of digested food fatty acids and glycerol  recombine to fat molecules and enter lacteal ii) i nto the lacteal

11. digested fats Absorption of digested food ii) i nto the lacteal

12. all parts of the body Absorption of digested food ii) i nto the lacteal

14. Absorption in small intestine -most of the digested food - most water undigested and unabsorbed materials large intestine

15. longitudinal section of a villus

16. 1999 HKCEE cross section of a villus 1) lacteal 2) blood capillary

17. 象皮病 (elephantiasis)

19. blood capillary lacteal wall of villus lumen Conclusion cross section of a villus