1. Announcements
Tomorrow’s quiz on NEJM paper
Bring two questions about NEJM
Exam I provided today

2. Which of the following enzymes work most effectively at a very low pH?
Salivary amylase
Trypsin
Pepsin
Pancreatic amylase
Pancreatic lipase

3. In zero gravity environment of space, how does food swallowed by an astronaut reach her stomach?
Swallowing hard
Running around wheel creates -> artificial gravity
Involuntary muscle contractions
IV administration of nutrients

4. Which of the following organs is incorrectly paired with its function?
Stomach –protein digestion
Oral cavity -starch digestion
Large intestine –bile production
Small intestine –nutrient absorption
Pancreas –enzyme production

6. Salivary glands Secretes enzymes that digest carbohydrates
1. Mouth Mechanical and chemical processing (chewing reduces size of food; saliva digests carbohydrates)
Salivary glands Secretes enzymes that digest carbohydrates
Liver Secretes molecules required for digestion of fats
2. Esophagus Transports food
3. Stomach Mechanical and chemical processing (digestion of proteins)
Gall bladder Stores secretions from liver; empties into small intestine
4. Small intestine Chemical processing and absorption (digestion of proteins, fats, carbohydrates; absorption of nutrients and water)
Figure 40.7 The Alimentary Canal
Caption:
The alimentary canal is a tube that runs from the mouth to the anus. The salivary glands, liver, gallbladder, and pancreas are not part of the canal itself. Instead, they secrete material into the tube at specific points.
Pancreas Secretes enzymes and other materials into small intestine
5. Large intestine Water absorption and feces formation

7. Stomach End of esophagus Sphincter seals off stomach from small
stomach from esophagus
Sphincter seals off
stomach from small
intestine
Figure: 40.8a
Caption:
The stomach is a muscular outpocketing of the alimentary canal. Muscle contractions mix food and break it into smaller pieces. 
Layers
of muscle
Beginning of
small intestine
Lumen
(interior)

8. Stomach lining Canal empties to lumen Parietal cells (secrete HCl)
Chief cells
(secrete pepsinogen)
Figure: 40.8b
Caption:
This transmission electron micrograph shows a section through the stomach wall.
Exercise: In part (b), draw the route of molecules and ions secreted by parietal and chief cells.

9. Secretion of HCI by parietal cells
HCl
to lumen
CO H2O
H2CO3
To blood H+ H+
HCO3–
HCO3– K+
H+/K+ pump
Cl–
Figure: 40.8c
Caption:
According to available data, this is how parietal cells secrete hydrochloric acid.   Exercise: In part (c), label the reaction catalyzed by carbonic anhydrase.
Cl–
Cl–
Cl–
Chloride channel
From blood
Canal empties
to lumen
Parietal cell

10. Enzymes, Hormones, other?
Enzymes: pepsinogen (inactive)-> pepsin (protease) from chief cells
Other: HCl -> denature ECM bacteria, from parietal cells, activator of pepsin
Other: Mucins/mucus protective from goblet or mucus cells
Other: mechanical churning -> acid chyme
Hormones: Gastrin (+), CCK/secretin (-), enterogastrone (-- pyloric sphinct)

11. Enzymes, Hormones, other?
Your turn

13. DIGESTION OF LIPIDS IN SMALL INTESTINE
Glycerol
Lipase
Fatty acids
1. Large fat globules are not digested efficiently by lipase.
2. Bile salts (produced in liver) act as
emulsifying agents.
3. Small fat droplets result from emulsification.
4. Lipase digests the small fat droplets into glycerol and free fatty acids.
Figure 40.10
Caption:
Bile salts are small lipids that act as emulsifying agents. Once they break up large fat globules, lipase can digest fats efficiently.

14. Cross-section of small intestine
Fold
Villi
Figure: left
Caption:
The transmission electron micrograph shows a cross section through the small intestine.
115 µm
Cross-section of small intestine

15. Lumen of small intestine
Apical side
Na+/glucose cotransporter
H2O
Osmosis
Na+
Glucose K+
GLUT-2 transport protein
Na+/K+-ATPase K+
ATP
Basolateral side
ADP
Blood
H2O
Na+
Glucose
Osmosis

18. Capillaries are small and extremely thin walled.

19. Insulin causes cells in the liver and skeletal
Glycogen
Glucose
Insulin causes cells in the liver and skeletal
muscle to synthesize glycogen; fat storage
cells synthesize triglycerides.
Pancreas secretes
INSULIN
If glucose
levels too high
Glucose
levels fall
HOMEOTASIS
(normal glucose
levels in blood)
If glucose
levels too low
Glucose
levels rise
Figure 40.13 
Caption:
Insulin and glucagon are both secreted by cells in the pancreas, but have opposite effects on blood glucose concentrations.  EXERCISE Draw a large X through the arrow that is disrupted in individuals with diabetes mellitus. Next to the X, jot notes indicating the nature of the defect in individuals with type I diabetes mellitus versus type II diabetes mellitus.
Pancreas secretes
GLUCAGON
Glucagon causes cells in liver and skeletal
muscle to catabolize glycogen; fat storage
cells catabolize fatty acids.
Glucose
Glycogen