## Anatomy of Gastric Glands and Acid Secretion **Key Point:** The fundic (oxyntic) glands are the primary source of gastric acid secretion, located predominantly in the fundus and body of the stomach. ### Fundic Glands — Structure and Function Fundic glands contain three main cell types: 1. **Parietal cells (oxyntic cells)** — secrete HCl and intrinsic factor 2. **Chief cells (peptic cells)** — secrete pepsinogen 3. **Mucous neck cells** — secrete mucus These glands extend deep into the gastric mucosa and are responsible for ~99% of gastric acid production. ### Comparison of Gastric Gland Types | Gland Type | Location | Primary Secretion | Acid Production | | --- | --- | --- | --- | | **Fundic (oxyntic)** | Fundus, body | HCl, pepsinogen, mucus | **Maximal** | | Pyloric | Antrum, pylorus | Mucus, gastrin, somatostatin | Minimal | | Cardia | Cardia (junction) | Mucus | None | | Gastric pits | Surface epithelium | Mucus | None | **High-Yield:** Fundic glands occupy ~75% of the gastric mucosa and are the exclusive site of parietal cell concentration, making them the dominant acid-secreting region. **Clinical Pearl:** Damage to fundic glands (as in autoimmune gastritis or extensive intestinal metaplasia) leads to achlorhydria and vitamin B₁₂ malabsorption due to loss of intrinsic factor. ### Regulation of Acid Secretion Parietal cell activation occurs via three pathways: 1. **Acetylcholine (ACh)** — vagal stimulation → M₃ receptors → ↑ acid 2. **Gastrin** — from pyloric G cells → CCK-B receptors → ↑ acid 3. **Histamine** — from enteroendocrine cells → H₂ receptors → ↑ acid **Mnemonic:** **GAH** = **G**astrin, **A**cetylcholine, **H**istamine — the three stimulators of parietal cell acid secretion.
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