Human Digestive System Overview

Introduction

• Average human food consumption:
  • 1 to 2.7 kg/day
  • 365 kg/year
  • Over 28,800 kg/lifetime
• Digestive system:
  • Comprises 10 organs
  • Spans 9 meters
  • Contains 20+ specialized cell types
  • Functions to convert food into nutrients and energy

Main Components of the Digestive System

1. Gastrointestinal Tract (GI Tract):
   • Twisting channel transporting food
   • Internal surface area: 30 - 40 square meters
2. Pancreas, Gallbladder, and Liver:
   • Break down food with special juices
3. Enzymes, Hormones, Nerves, and Blood:
   • Work together to break down and modulate digestion
4. Mesentery:
   • Tissue that supports digestive organs in the abdomen

Digestive Process

1. Preparation

• Begins before food reaches the tongue
• Saliva production:
  • Glands produce 1.5 liters/day
  • Saliva mixes with food forming a bolus

2. Esophagus

• 25 cm long tube
• Peristalsis: muscular contractions push food to the stomach

3. Stomach

• Muscular walls break bolus into chunks
• Release of acids and enzymes to dissolve food and proteins
• Hormones signal production of digestive juices and bile

4. Small Intestine

• Duodenum:
  • Bile dissolves fats in chyme
  • Pancreatic and intestinal juices break down fats into fatty acids and glycerol
• Jejunum and Ileum:
  • Enzymes break proteins into amino acids, carbohydrates into glucose
  • Villi increase surface area for absorption into bloodstream

5. Large Intestine (Colon)

• Absorbs remaining fluids
• Forms stool from leftover fiber, water, and cells
• Stool is stored in the rectum until expelled

Conclusion

• Digestion process takes 30-40 hours
• Final expulsion of waste through the anus completes the digestive process