Page 205 - Physiology and Pathophysiology MNU 2024-2025 نظرى

Clinical pharmacy 2024/2025 Level 2 Pharm D Physiology and Pathophysiology (MD303)
1. Hydrochloric acid (HCl),

Functions of HCl include:
a. Activation of pepsinogen  pepsin
b. Assisting in breakdown of connective tissue & muscle fibers

within ingested food
Parietal cells c. Killing of most types of microorganisms ingested with food.

2. intrinsic factor

• Essential for the absorption of vitamin B12
• Any defect in the production of intrinsic factor (as in

gastrectomy)  no vit B12 absorption  pernicious anemia.
Pepsinogen

• Activated within the lumen of the stomach by HCl into
pepsin.
Chief cells
• Optimally active at an acidic pH (pH = 2),

• Pepsin begins protein digestion by fragmenting proteins into
smaller peptide chains.

HCl production

1. Parietal cells contain carbonic anhydrase enzyme (CAH):

+
+
+
2. H produced is pumped out of parietal cells by H /K ATPase pump (proton pump).
-
-
3. HCO 3 in parietal cells is exchanged for Cl in blood.
+
-
4. Cl is pumped out to join H  forming HCl in the gastric lumen.

2. Pyloric gland area:
located in the remaining distal 20% of the stomach.

G cells

• Releases gastrin into the blood  carried back to the stomach.

• The major function of gastrin  enhance acid secretion by:
a. directly stimulating parietal cells  HCl

b. Stimulates the local release of histamine from enterochromaffin- like cells in
the wall of the stomach  stimulates parietal cells to release HCl.

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