Basics of Gastric Acid Secretion for Esproute

1. Physiology of Gastric Acid Secretion

2. Introduction
• Parietal cells: Predominate in the oxyntic glands, secrete hydrochloric acid and intrinsic factor
• Chief cells: Located at the base of the oxyntic glands, are responsible for secreting the
digestive enzyme precursor pepsinogen
• Neuroendocrine cells containing hormonal and paracrine signaling agents that regulate the
activity of the parietal cell reside within the glands. These include D cells, enterochromaffin-
like (ECL) cells, A-like cells and enterochromaffin (EC) cells
Oxyntic Gland Area: 80%
Pyloric Gland Area: 20%
Stomach

3. Gastric Gland
Stomach mucosa’s epithelial lining consists of number of
gastric pits, leading to gastric gland

4. Gastric Gland: Secretions
Cell Types Substances Secreted Function
Parietal Cells HCL
Intrinsic Factor
Kills microbes & activates pepsinogen
Binds vitamin B12 to help it absorption
Chief Cells Pepsinogen (converted to pepsin by acid)
Gastric Lipase
Protein Digestion
Fat Digestion
G Cells Gastrin Stimulates acid secretion
ECL Cells Histamine Stimulates acid secretion
Mucus-neck Cells Mucus & Bicarbonate Protection from acid
D Cells Somatostatin Inhibits acid secretion

5. Gastric Gland: Gastric Juice
• Pale yellow in colour, pH is 1-3
• Per day secretion is 2-3 liters
It is a colourless, watery, acidic, digestive fluid produced in the stomach
Gastric Juice
• HCl
• Electrolytes
• Mucus,
• Water
• Intrinsic factor
• Bicarbonate
Gastric glands secretes a complex digestive fluid
referred to as gastric juice

6. Gastric Gland: Gastric Juice Functions
Hydrochloric Acid (HCl)
Converts pepsinogen to pepsin for chemical
digestion
• Provides optimal pH environment for
pepsin
• Destroys some bacteria
• Stimulates the small intestinal mucosa to
release Secretin and CCK
• Promotes the absorption of Ca2+ and Fe2+
in small intestine

7. Gastric Gland: Gastric Juice Functions
Pepsinogen (precursor of pepsin)
• Digestion of proteins
Mucus
• Forms a protective barrier: Mucus-
bicarbonate barrier
Intrinsic factor
• Combines with vitamin B12 to make it
absorbable

8. Parietal Cell
Proton Pump (H+K+-ATPase) : Membrane protein in the parietal cells
Parietal Cell

9. How is Gastric Acid produced?
Sight, smell, taste and eating of food leads
to release of biochemical substances Biochemicals get attached to respective
receptors on parietal cell
Activation of proton pump and release of HCl
Step 1 Step 2
Step 3
Gastrin
Histamine
Acetylcholine

10. Proton Pump Inhibitors: Mechanism
Proton Pump Inhibitors
Block H+K+-ATPase
Inhibit acid production

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