Digestion lecture

1
Digestion lecture

• ANP 128

2

• OBJECTIVES
• How does the structure of the digestive system
  aid in its function?
• What are the secretions of the mouth, stomach,
  small intestine, pancreas, liver, and large
  intestine?
• How are these secretions used?
• What absorption takes place in the mouth,
  stomach, small intestine, pancreas, liver, and
  large intestine?
• Why is the chemical structure of nutrients
  important in the manner of breakdown and
  absorption?

3

• Histology
• 4 layers
• serosa
• muscularis
• submucosa
• mucosa

4
Mouth
5
Esophagus
6
Gastric Secretions

• works on Chyme
• Acid HCl
• Intrinsic Factor
• G cells secrete gastrin
• Mucus
• peptidases
• Gastric lipase
• Gastric motility

7
Small Intestine Secretions

• Mucus
• Bicarbonate
• Brush border enzymes

8
Pancreas

• Pancreas - sodium bicarbonate and digestive
  enzymes
• 1200L/day
• Enzymes
• proteases
• phospholipases
• pancreatic amylase
• Activation of Enzymes - most enzymes need to be
  activated
• Sodium bicarbonate ? pH 7 stops action of
  pepsin
• Regulation of Secretions - nervous and hormonal

9
Liver secretes Bile into gallbladder

• Bile
• components
• bile acids
• bile salts
• cholesterol
• bilirubin
• sodium bicarbonate
• Emulsifies fats through salts and cholesterol --gt
  micelles

10
Large Intestine

• Peristalsis
• Bacteria activity
• Water reabsorbed

11
Absorption

• Water
• 1. Small Intestine
• 2. Large Intestine
• 3. Amount depends upon speed
• 4. Laxatives w/Mg are not absorbed and retain
  water

12
Absorption

• Carbohydrates
• Monosaccharides

13
Absorption

• Protein
• 1. peptidases
• 2. pancreas and small intestine w/brush border
  enzymes
• 3. Movement w/Na
• 4. Once inside - moving down concentration
  gradient into capillaries
• 5. then onto the liver

14
Absorption

• Fats
• Lipases in small intestine
• Micelles
• Bile salts
• Diffuses into epithelial cells
• Cholymicrons

15
Absorption

• Electrolytes
• Na
• Cl-
• Ca2
• Fe, K, MG, PO4-

16
Absorption

• Vitamin
• A D E K
• B and C by diffusion
• B12 combines w/intrinsic factor

17

• Questions?