SUMMARY 161 



Summary. — Digestion is the process by means of which foods 

 are prepared to become part of the blood. This is brought 

 about by enzymes, agents which cause complex foods to break down 

 into simple forms which are capable of absorption through the 

 cells lining the food tube. 



The table on page 160 sums up the process of digestion in the 

 human body. 



Absorption takes place mostly in the small intestine by means 

 of very numerous absorbing organs called villi. Absorption is 

 more than diffusion or osmosis, as the cells of the villus appear to 

 have a selective action on the solutes absorbed. 



Problem Questions 



1. How is digestion brought about? 



2. What is an enzyme? How is it made? How does it work? Name 

 some enzymes and give their functions. 



3. Compare the mouth of the frog and of man in all respects. 



4. Discuss the teeth as to function, structure, and care. 



5. What is the function of the tongue in digestion ? Of the saUvary glands ? 



6. What are the functions of the stomach ? How are they accomphshed ? 



7. What are hormones and what do they do? 



8. What is secretin and how does it function? 



9. Why is the pancreas considered the most important digestive gland? 



10. What are the fimctions of the liver? 



11. What is glycogen and where is it made? 



12. What is the result of final digestion on foods? 



13. How and where is food absorbed ? 



Peoblem and Project References 



Hunter, Laboratory Problems in Civic Biology. American Book Company. 



Burton-Opitz, Physiology. W. B. Saunders Company. 



Cohnheim, Enzymes. John Wiley and Sons. 



Harrow, Glands in Health and Disease. E. P. Du^ton and Company. 



Martin, The Human Body, Advanced Course. Henry Holt and Company. 



Schafer, The Endocrine Organs. Longmans, Green and Company. 



Starling, Principles of Human Physiology. Lea and Febiger. 



Stiles, Nutritional Physiology. W. B. Saunders Compan3^ 



XJnderhill, The Physiology of the Amino-acids. Yale University Press. 



Williams, Anatomy and Physiology. W. B. Saunders Company. 



