Human stomach:
Structure
1. Location: The stomach is located in the upper left region of the abdominal cavity, below the diaphragm.
2. Shape: The stomach is a sac-like organ, shaped like a curved tube.
3. Size: The stomach can hold approximately 1-2 liters of food and liquid.
4. Layers: The stomach wall consists of four layers:
1. Mucosa (innermost layer)
2. Submucosa
3. Muscularis
4. Serosa (outermost layer)
Functions
1. Mechanical Digestion: The stomach muscles churn and mix food with digestive enzymes.
2. Chemical Digestion: The stomach lining secretes digestive enzymes, such as pepsin and gastric amylase, to break down proteins and carbohydrates.
3. Protein Denaturation: The stomach's acidic environment denatures proteins, making them more accessible to digestive enzymes.
4. Absorption: The stomach absorbs some nutrients, such as alcohol and certain medications.
Regions
1. Cardiac Region: The upper portion of the stomach, near the esophagus.
2. Fundus: The upper curvature of the stomach.
3. Body: The main portion of the stomach.
4. Antrum: The lower portion of the stomach, near the pylorus.
5. Pylorus: The narrow region that connects the stomach to the small intestine.
Digestive Process
1. Gastric Juice Secretion: The stomach lining secretes gastric juice, containing digestive enzymes and acid.
2. Food Mixing: The stomach muscles churn and mix food with gastric juice.
3. Protein Breakdown: Pepsin breaks down proteins into smaller peptides.
4. Carbohydrate Breakdown: Gastric amylase breaks down carbohydrates into simpler sugars.
5. Chyme Formation: The partially digested food mixture is called chyme.
6. Pyloric Sphincter Relaxation: The pyloric sphincter relaxes, allowing chyme to enter the small intestine.
Regulation
1. Hormonal Regulation: Hormones like gastrin, secretin, and cholecystokinin regulate stomach function.
2. Nervous System Regulation: The vagusnerve and enteric nervous system regulate stomach contractions and secretions.
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