THE HUMAN DIGESTIVE SYSTEM
Physical and Chemical Digestion in the Mouth (pages 408 - 409)
1. What structures are in our mouth for physical digestion? _____________
2. State the role of
a) incisors: __________________________________
b) canines: __________________________________
c) premolars: _______________________________
d) molars: __________________________________
3. Why do herbivores have more molars than carnivores? ________________________
_______________________________________________________________________
4. What enzyme does saliva have? ________________
5. Describe the chemical digestion that this enzyme is involved in.
________________________________________________________________________
6. What else does saliva contain? _______________ why? ______________________
________________________________________________________________________
7. Once swallowed, food travels from the mouth to the stomach by way of a long tube
called the ___________________________
8. The bolus of food stretches the walls of the esophagus, activating smooth involuntary
muscles that set up waves of contractions called ________________________.
The Structure of the Stomach (pages 409 - 410)
9. a) Which nutrient is partly digested in the stomach? _______________
b) Which nutrients are not digested here? _________________________
10. What controls the movement of food into and out of the stomach?
____________________
11. The semi-liquid mixture of food and gastric juice is called
____________
12. Nerves detect when food is present and release which hormone?
______________________________
13. This hormone stimulates the release of gastric juice which is made up of
mucus, acid and digestive enzymes. What is the purpose of the mucus?
____________________________________________________________
14. What is the range of pH of the acid in gastric juice? _______________
15. The acid converts the inactive enzyme pepsinogen to its active form
pepsin. What is the role of pepsin? ________________________________
_____________________________________________________________
The Structure of the Small Intestine (pages 412 - 413)
16. How long is our small intestine? ______ how wide? _______________
17. Name the three parts of the small intestine; ____________________,
_____________________ and ________________.
18. a) In which part does most of the digestion occur? _________________
b) In which part does most of the absorption occur? ________________
19. Describe how villi and microvilli increase the surface area of the small
intestine for the absorption of nutrients.
20. Within each villus,
a) where do digested fats get transported? ___________________________
b) where do all other nutrients enter the bloodstream? _________________
The Role of the Pancreas in Digestion (page 414 – 416)
21. When chime enters the duodenum from the stomach, the hormone
cholecystokinin (CCK) is secreted.
a) What does CCK signal the pancreas to do? ___________________
_____________________________________________________________
_____________________________________________________________
b) What does CCK signal the stomach to do?
_____________________________________________________________
22. Secretin is another hormone that stimulates the release of bicarbonate
ions from the pancreas. What is their role?
_____________________________________________________________
23. Copy Figure 6 on page 415 below which summarizes the breakdown of
proteins into amino acids.
24. The pancreas also secretes lipases. What group of nutrients do lipases
break down? ___________.
The Liver and Gall Bladder (page 416)
25. What is the digestive function of the liver?
__________________________________________________________
26. What does bile do? Why is this step important?
_____________________________________________________________
_____________________________________________________________
27. What is the function of the gall bladder?
_____________________________________________________________
The Structure and Function of the Large Intestine (page 418 – 419)
28. The large intestine is only 1.5 m long but is quite large in diameter.
How large is it in diameter? ________
29. What substances are absorbed by the large intestine back into the body?
_____________________________________________________________
30. What is the role of bacteria in the large intestine?
_____________________________________________________________
Egestion
31. Why is fibre important in our diet?
_____________________________________________________________
_____________________________________________________________
32. Nerves in the walls of the large intestine detect the movement of feces
into the rectum. Feces are then eliminated through the anus. How are the
anal sphincters controlled?
_____________________________________________________________
_____________________________________________________________
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