Gastrointestinal Hormones: Key Regulators of Digestion for the DAT
The digestive system is regulated by specialized hormones that control stomach acid secretion, enzyme release, and nutrient absorption. Understanding these hormones is essential for DAT biology, as they appear in questions about homeostasis, digestion, and endocrine signaling. This blog breaks down the key gastrointestinal (GI) hormones and their roles in digestion.
Key Gastrointestinal Hormones
The major GI hormones are:
| Hormone | Source | Function |
|---|---|---|
| Gastrin | Stomach (G cells) | Stimulates HCl secretion and gastric motility |
| Secretin | Duodenum (S cells) | Stimulates bicarbonate release, inhibits gastric acid secretion |
| Cholecystokinin (CCK) | Small Intestine (I cells) | Stimulates bile release and pancreatic enzyme secretion |
| Ghrelin | Stomach | Stimulates hunger and food intake |
| Motilin | Small Intestine (M cells) | Stimulates peristalsis |
| Gastric Inhibitory Peptide (GIP) | Small Intestine (K cells) | Stimulates insulin secretion, inhibits gastric emptying |
Hormone Actions & Digestion Regulation
1. Gastrin: The Stomach Acid Booster
Released in response to food (especially proteins).
Increases HCl secretion from parietal cells, aiding protein digestion.
Stimulates stomach motility, promoting mechanical breakdown.
2. Secretin: The Acid Neutralizer
Triggered by acidic chyme entering the small intestine.
Stimulates the pancreas to release bicarbonate (HCO₃⁻) to neutralize stomach acid.
Inhibits gastric acid secretion to prevent excessive acidity.
3. Cholecystokinin (CCK): Fat & Protein Digestor
Released in response to fats and proteins in the small intestine.
Stimulates bile release from the gallbladder (for fat digestion).
Triggers pancreatic enzyme secretion, including lipases and proteases.
4. Ghrelin: The Hunger Hormone
Released when the stomach is empty, signaling hunger to the brain.
Increases food intake and gastric motility to prepare for digestion.
5. Gastric Inhibitory Peptide (GIP): The Insulin Booster
Triggered by glucose and fatty acids in the small intestine.
Stimulates insulin release from the pancreas.
Inhibits gastric motility and acid secretion to slow digestion.
DAT-Style Question Example
A patient with a gallbladder disorder has difficulty digesting fats. Which hormone is likely involved?
A) Gastrin
B) Secretin
C) Cholecystokinin (CCK)
D) Ghrelin
Answer: C) Cholecystokinin (CCK) – It stimulates bile release, which is essential for fat digestion.
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Conclusion
Gastrointestinal hormones play a crucial role in digestion and are a high-yield topic on the DAT. By mastering the functions of gastrin, secretin, CCK, and others, you’ll be prepared to tackle endocrine and digestion-related questions with confidence!
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