1. Gastric Secretions
Sarah and Susan
07/10/2014

2. Stomach Anatomy

3. The Pyloric Sphincter
A ring of smooth muscle and connective tissue between the gastric antrum and the duodenum.
Has 2 Functions:
Allows the regulated emptying of gastric contents at a rate consistent with the ability of the duodenum to process chyme.
Prevents the regurgitation of duodenal contents back into the stomach

4. Gastric Juice
How many litres of gastric juice are produced by the stomach each day?
300ml
500ml 1L 3L 5L

5. Gastric Juice What are the main components of gastric juice? (4)
Hydrochloric acid (HCl)
2. Mucus
3. Enzymes: pepsinogens, gastric lipase
4. Intrinsic Factor

6. What are the major types of secretory epithelial cells in the stomach?
Surface mucous cell
Mucous neck cell
Parietal cell
Chief cell
G cell
Enterochromaffin-like (ECL) cell
Delta (D) cell
Mucus
HCl and IF
Pepsinogen
Gastrin
Histamine
Somatostatin

7. Mucus What is it? What is the Gastric Mucosal Barrier?
A mixture of glycoproteins and glycopolysaccharides.
What is the Gastric Mucosal Barrier?
Mucus and the alkaline secretions entrapped within it.
It protects the stomach against acid, proteolytic enzymes and mechanical damage.

8. Hydrochloric Acid Produces a gastric luminal pH of 1-2
Stimuli of acid secretion also promotes increased mucus and HCO3- secretion.
Stimulated by:
gastrin
acetylcholine
histamine
Inhibited by:
somatostatin
prostaglandins E2 and I2
enteric hormones

10. Inhibition of Gastric Acid Secretion
ECL
cell
Somatostatin -
SSR
Cholinergic
nerve
Blood vessel
Muscarinic-R
Gastrin-R + +
Histamine
ACh
Gastrin + -
Somatostatin + +
Muscarinic-R
H2-R
Gastrin-R +
PGE2-R -
SSR
PGE2 -
Parietal cell K+ H+
Cl- P C AA H+
Cl- K+

11. The Parietal Cell
1. Truncated pyramidal shape, with apex oriented towards gastric lumen.
2. Canaliculi (envaginations of luminal membrane) lined with ion pumps: increased surface area
3. Many mitochondria: provides energy for H+ pump

12. The Parietal Cell 4
CO2 and H2O are converted into H+ and HCO3- by carbonic anhydrase
H+ is pumped into the lumen by a H+/K+-ATPase transporter
HCO3- leaves the cell and enters the bloodstream via antiport with Cl-.
Cl- diffuses passively into the lumen via a Cl- channel. 2 1 3

13. Intrinsic Factor Glycoprotein secreted by parietal cells
Intrinsic factor production is the only indispensable function of the stomach.
Is essential for the absorption of vitamin B12 in the intestines.

14. Pepsinogen Pepsin secretion parallels acid secretion.
Parietal Cell
HCl
Chief Cell
Pepsinogen
Pepsin
Protein
Peptide
Pepsin secretion parallels acid secretion.
Pepsin is active only at low pH.

15. Gastric Hormones Hormone Production Site Gastric Functions Gastrin
G cells in antrum of stomach
Stimulates Acid Secretion
Stimulates Gastric Motility
Inhibits Gastric Emptying
Stimulates Intestinal Motility
Histamine
ECL cells in gastric mucosa
Increases Local Blood Flow
Somatostatin
D cells in antrum and body of stomach
Inhibits Gastrin
Inhibits Acid Secretion

16. What is the one indispensable function of the stomach?
SECRETION OF INTRINSIC FACTOR