Digestive System Overview

1. Introduction to Digestion

• Digestion begins in the mouth as soon as food is consumed.
• Mechanisms Involved:
  • Teeth break down food mechanically.
  • Saliva contains enzymes like salivary amylase, which begins breaking down starch into simpler forms.

2. Formation of Bolus

• Chewing and enzyme activity convert food into a bolus, making it easier to swallow.

3. Esophagus and Peristalsis

• The bolus moves down the esophagus to the stomach.
• Peristalsis:
  • Muscle contractions that push the bolus towards the stomach.

4. Stomach Functions

• The bolus enters the stomach via the lower esophageal sphincter.
• Stomach Processes:
  • Secretes gastric juices including hydrochloric acid (pH 1.5 to 2.0).
  • Muscular layers mix the contents, turning food into a paste called chyme.

5. Small Intestine

• Chyme enters via the pyloric sphincter.
• Structure and Function:
  • Approximately 6 meters long.
  • Absorbs about 90% of nutrients.
  • Composed of three parts: duodenum, jejunum, and ileum.
• Nutrient Absorption:
  • Villi absorb nutrients into the bloodstream.

6. Role of Liver, Pancreas, and Gallbladder

• Liver:
  • Produces bile for fat breakdown.
  • Removes toxins, stores vitamins and minerals.
• Pancreas:
  • Produces enzymes for breaking down carbohydrates, fats, and proteins.
• Gallbladder:
  • Stores bile, releases it when needed.

7. Large Intestine

• Structure and Function:
  • Around 2 meters long with five parts: cecum, ascending colon, transverse colon, descending colon, sigmoid colon.
  • Absorbs water and electrolytes.
  • Gut bacteria further break down food.

8. Feces Formation and Excretion

• Peristalsis moves feces toward the rectum.
• Rectum Function:
  • Stretch receptors signal the need for defecation.
  • Timely defecation prevents dry, hard feces (constipation).

9. Digestive Timeline

• Food takes about 30 hours to pass through the large intestine.
• Entire digestive process from swallowing to defecation takes approximately 2 to 4 days.

Conclusion

• Efficient digestion relies on a sequence of processes involving various organs and enzymes.

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