Understanding the Human Digestive System

Introduction

• Humans consume between 1 to 2.7 kg of food daily.
• Over a lifetime, this equates to more than 28,800 kg.
• The digestive system is complex, consisting of 10 organs and over 20 specialized cell types.

Main Components of the Digestive System

1. Gastrointestinal Tract
   • A twisting channel that transports food.
   • Internal surface area of 30-40 square meters.
2. Pancreas, Gallbladder, and Liver
   • Use special juices to break down food.
3. Enzymes, Hormones, Nerves, and Blood
   • Facilitate digestion and nutrient delivery.
4. Mesentery
   • Tissue that supports and positions digestive organs.

Digestive Process Overview

• Begins before food intake; saliva production starts in anticipation.
• Saliva: 1.5 liters produced daily, helps form a moist lump called bolus.

Mouth and Esophagus

• Chewing and saliva turn food into bolus.
• Bolus travels down the esophagus via peristalsis to the stomach.

Stomach

• Stomach walls muscle and break down bolus.
• Hormones trigger acid and enzyme release, starting protein breakdown.
• Prepares digestive juices and bile from pancreas, liver, and gallbladder.
• Transforms bolus into chyme over three hours.

Small Intestine

• Bile from gallbladder and liver dissolves fats in chyme in the duodenum.
• Pancreatic and intestinal juices break down fats, proteins, and carbohydrates.
• Villi in jejunum and ileum maximize absorption into the bloodstream.

Large Intestine (Colon)

• Remaining fiber, water, and dead cells proceed to the colon.
• Fluid absorbed; remaining mass forms stool.
• Stool moved to the rectum, expelled through the anus.

Conclusion

• The digestive journey typically lasts 3-5 years, converting food into essential nutrients and expelling waste.