What organs secrete substances into the small intestine and what do they secrete?
1. Liver:
- Bile: Bile salts help in the emulsification and digestion of fats.
- Cholesterol: Excess cholesterol is excreted into the bile.
2. Pancreas:
- Pancreatic enzymes:
- Amylase: Breaks down carbohydrates.
- Lipase: Breaks down fats.
- Proteases: Break down proteins into peptides and amino acids.
- Bicarbonate ions: Neutralizes the acidic chyme from the stomach, providing an optimum pH for pancreatic enzyme activity.
3. Small intestine itself:
- Brunner's glands: Secrete alkaline mucus that helps neutralize stomach acid and protect the intestinal lining.
- Crypts of Lieberkühn:
- Enterocytes: Secrete digestive enzymes such as lactase, sucrase, and maltase, which break down carbohydrates.
- Goblet cells: Secrete mucus that lubricates the intestinal lining and protects it from digestive enzymes.
- Paneth cells: Secrete antimicrobial peptides that help maintain the balance of gut microbiota.
- Enteroendocrine cells: Secrete hormones such as cholecystokinin (CCK) and gastrin, which regulate digestion and satiety.
4. Stomach:
- Gastrin: Stimulates the secretion of gastric juices and hydrochloric acid from the stomach, which helps in the initial digestion of proteins.