Announcements

1
Announcements

• Tomorrows 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?

1. Salivary amylase
2. Trypsin
3. Pepsin
4. Pancreatic amylase
5. Pancreatic lipase

3
In zero gravity environment of space, how does
food swallowed by an astronaut reach her stomach?

1. Swallowing hard
2. Running around wheel creates -gt artificial
   gravity
3. Involuntary muscle contractions
4. IV administration of nutrients

4
Which of the following organs is incorrectly
paired with its function?

1. Stomach protein digestion
2. Oral cavity -starch digestion
3. Large intestine bile production
4. Small intestine nutrient absorption
5. Pancreas enzyme production

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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)
4. Small intestine Chemical processing and
absorption (digestion of proteins, fats,
carbohydrates absorption of nutrients and water)
Gall bladder Stores secretions from liver
empties into small intestine
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 esophagus
Sphincter seals off stomach from small intestine
Layers of muscle
Lumen (interior)
Beginning of small intestine
8
Stomach lining
Canal empties to lumen
Parietal cells (secrete HCl)
Chief cells (secrete pepsinogen)
9
Secretion of HCI by parietal cells
HCl to lumen
CO2 H2O
H2CO3
To blood
H
H
HCO3
HCO3
K
H/K pump
Cl
Cl
Cl
Cl
Chloride channel
From blood
Canal empties to lumen
Parietal cell
10
Enzymes, Hormones, other?

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

11
Enzymes, Hormones, other?

• Your turn

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DIGESTION OF LIPIDS IN SMALL INTESTINE
Glycerol
Lipase
Fatty acids
4. Lipase digests the small fat droplets into
glycerol and free 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.
14
Fold
Villi
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
Glucose
Na
Osmosis
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Capillaries are small and extremely thin walled.
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Glycogen
Glucose
Insulin causes cells in the liver and
skeletal muscle to synthesize glycogen fat
storage cells synthesize triglycerides.
Pancreas secretes INSULIN
Glucose levels fall
If glucose levels too high
HOMEOTASIS (normal glucose levels in blood)
Glucose levels rise
If glucose levels too low
Pancreas secretes GLUCAGON
Glucagon causes cells in liver and
skeletal muscle to catabolize glycogen fat
storage cells catabolize fatty acids.