1. Gastrointestinal System
Physiology Review

2. The Job of the Bowel
• Food:
– Movement
– Breakdown
– Absorption
• Keeping dangerous gut contents out of the blood
• Keeping blood contents from being lost into the gut
lumen

3. • <insert figure xxx>

4. Bowel and Mesenteries

5. Question
Tell whether the following statement is true or
false.
The mesentery contains the intestine’s blood
supply.

6. True Answer
An extension of the visceral peritoneum, the
mesentery contains blood vessels that supply
oxygen and nutrients to (arteries) and
eliminate CO2 and waste from (veins) the
intestines.

7. Prader-Willi Syndrome
• Plasma ghrelin levels are extremely high
Discussion:
• What are the effects of this disorder?

8. Scenario
A woman has a pancreatic tumor that secretes
gastrin.
Question
• What complication is likely to develop? Why?

9. Scenario
• A man cannot produce cholecystokinin.
Question
• What problems will this cause him?

10. Carbohydrate Digestion
• Mouth: Salivary amylase
• Duodenum: pancreatic amylase
– Polysaccharides  disaccharides
• Brush border enzymes
– Disaccharides  monosaccharides
– Monsaccharides absorbed into blood

11. Protein Digestion
• Stomach: pepsinogen
– Activated to pepsin by acid in stomach
– Breaks proteins into polypeptides
• Duodenum: pancreatic trypsinogen
– Activated to trypsin in duodenum
– Breaks proteins into polypeptides
• Brush border enzymes
– Breaks polypeptides into 2–3 amino acid peptides
– Peptides absorbed into blood

12. • Duodenum: bile Fat Digestion
– Emulsifies fats
• Duodenum: pancreatic lipase
– Breaks triglycerides into glycerol and fatty acids
• Jejunum
– Packages digested fats as chylomicrons
– Passed to the lymph

13. Question
Digestion of which substance begins in the
mouth?
b. Carbohydrates
c. Protein
d. Fat
e. All of the above

14. a. Carbohydrates Answer
Carbohydrate digestion begins in the mouth
with salivary amylase; protein digestion
begins in the stomach with pepsinogen; fat
digestion begins in the small intestine with
bile and pancreatic lipase.

15. Discussion
Which is the best choice to reduce fat digestion?
• Suppress duodenal hormone secretion
• Suppress the activity of chief cells in the stomach
• Decrease intrinsic factor secretion
• Block gall bladder contraction
• Inactivate pancreatic lipase

16. Question
How would fat digestion be affected if bile levels
decreased?
b. It would increase.
c. It would decrease.
d. It would have no effect—fat digestion is mainly
affected by amylase.
e. It would have no effect—fat digestion is mainly
affected by lipase.

17. Answer
a. It would decrease.
Bile emulsifies fat so that it can be more easily
digested. Decreased amounts of bile would
lead to decreased fat emulsification and
decreased ability to break down/digest fats.