Overview of the Digestive System

Function of the Digestive System

• Breaks down food into tiny pieces for absorption into body cells.
• Primarily used for energy to support movement and metabolism.
• Key nutrients:
  • Carbohydrates (starch, glucose)
  • Proteins
  • Fats

Process of Digestion

• Involves physical and chemical breakdown of food.

Mouth

• Food is broken down physically by chewing.
• Salivary glands release saliva which:
  • Makes the mixture more liquid.
  • Contains salivary amylase (enzyme) that begins carbohydrate breakdown.

Esophagus

• Food is swallowed and passes down the esophagus into the stomach.

Stomach

• Muscular sac with three important functions:
  1. Mixes and pushes food around using muscular walls.
  2. Produces pepsin (protease enzyme) to break down proteins.
  3. Produces hydrochloric acid to kill bacteria and create an ideal environment for pepsin.
• After about an hour, food is squeezed into the small intestine.

Small Intestine

• Main site for digestion and absorption of nutrients.
• Produces digestive enzymes.
• Pancreas:
  • Produces most digestive enzymes, released into small intestine as pancreatic juices.
• Gallbladder:
  • Releases bile, which:
    • Neutralizes stomach acid (bile is alkaline).
    • Emulsifies fats, breaking them into tiny droplets for better enzyme action.
• Bile is made in the liver and stored in the gallbladder.
• Nutrients are absorbed across the intestinal lining into the bloodstream.

Intestinal Lining

• Contains tiny finger-like projections called villi:
  • Increase surface area for absorption.
  • Have a single layer of surface cells for short diffusion distance.
  • Good blood supply maintains concentration gradient.

Large Intestine

• Absorbs excess water from leftover material.
• Remaining material becomes feces, stored in the rectum until removal.

Recap of the Digestive Process

1. Food enters the mouth, chewed and mixed with saliva.
2. Passes down the esophagus to the stomach.
3. Stomach mixes food, producing enzymes and acid.
4. Food moves to the small intestine, mixing with pancreatic juices and bile.
5. Nutrients are absorbed through the intestinal lining into the bloodstream.
6. Leftover material goes to the large intestine for water absorption, resulting in feces.

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Conclusion

• Summary of the digestive process from start to finish.
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