1. Stomach Anatomy and Activity
Cells of the Mucosa
Chemical Digestion
Control of Digestion
Be able to discuss the function of the major cell types found in the stomach.
Be able to discuss how pepsins and acid interact to promote protein digestion.
Be able to discuss how the three stages of controlling the stomach including excitatory and inhibitory effects.
Handout: Reflexes in the Stomach (in class)
Marieb: 23 1

2. Layers of the Stomach: Mucosa
Gastric Pits 2

3. Gastric Pits Produce Stomach Acid
Depths are lined with specialized cells 3

4. Parietal (Oxyntic) Cells
HCl
Intrinsic Factor
(needed for B12 absorption)
Decrease pH

5. Acids Denature Proteins

6. Gastric Juice Production
3L/Day
G Cells
Gastrin
Gastrin Inhibitors 6

7. Mucus Protects the Mucosa
Superficial Epithelial Cells
Bicarbonate
(HCO3-)
Absorbs protons
(H2CO3) 7

8. Protein Digestion in the Stomach
Denaturation
Pepsin
Rennin

9. Aka Zymogenic Cells
Produces Pepsinogen
Chief Cells

10. Pepsinogen  Pepsin Requires H+ Pepsin can activate Pepsinogen
Pepsin most efficient pH 10

11. Precursor Cells Replenish the Epithelium
Stem Cells
Stomach surface replaced every 3-6 days 11

12. Controlling Gastric Juice Levels
1. Cephalic
2. Gastric
3. Intestinal 12

13. Phase 1: Cephalic or Reflex Phase
1”-5” before food enters stomach
Small gastric acid release
+ Taste, thought of food
- Low appetite, depression,
Ghrelin

14. Phase 2: Gastric ENS, G Cells 3-4’, 2/3 of Gastric acid + Proteins
Increase pH
Distension
- Too low pH

15. Proteins Change pH 15

16. Phase 3: Intestinal Phase (Mostly Inhibitory)
Too much acid, protein, fats
Gastrin Inhibitors
CCK
Secretin 16

17. Phase 3: Intestinal Phase (Mostly Inhibitory)
Distention of SI
Pyloric sphincter closes 17

18. Mechanical Digestion and Distension
Cyclic Slow Waves: 3/minute
Stronger with distension
Stronger as you move distally through stomach

19. Pyloric Region: The Stomach’s Blender
Pyloric antrum
Stomach 30ml  SI
SI 27ml Stomach
Net 3ml/contraction 19