Digestive System Overview

Human Food Consumption

• Average human consumption: 1 to 2.7 kg of food per day
• Yearly consumption: over 365 kg per person
• Lifetime consumption: more than 28,800 kg

Digestive System Components

• Comprised of 10 organs, 9 meters in length
• Contains over 20 specialized cell types
• Main task: Convert food into nutrients and energy
• Four main components:
  1. Gastrointestinal Tract
     • Twisting channel transporting food
     • Internal surface area of 30-40 sq meters
  2. Pancreas, Gallbladder, and Liver
     • Break down food with special juices
  3. Enzymes, Hormones, Nerves, and Blood
     • Work together to digest food
     • Modulate digestive process and deliver nutrients
  4. Mesentery
     • Tissue supporting and positioning digestive organs

Digestive Process

Pre-Ingestion

• Saliva production begins with anticipation of food
• Daily saliva production: 1.5 liters

Ingestion and Initial Breakdown

• Chewing and saliva form a bolus
• Enzymes in saliva break down starch
• Bolus travels down the esophagus via peristalsis to the stomach

Stomach Processing

• Muscular stomach walls break bolus into chunks
• Hormones trigger release of acids and enzyme-rich juices
• Proteins begin breakdown
• Pancreas, liver, and gallbladder prepare digestive juices
• Bile produced for fat digestion

Small Intestine Processing

• Chyme formation after 3 hours in the stomach
• Bile from gallbladder enters duodenum
• Fats dissolved by bile for digestion
• Pancreatic and intestinal juices break down fats into fatty acids and glycerol
• Proteins and carbohydrates further broken down
• Absorption in jejunum and ileum with villi maximizing surface area
• Blood transports nutrients to organs and tissues

Large Intestine Processing

• Leftover fiber, water, and dead cells reach the colon
• Fluid absorbed through intestinal wall
• Formation of stool
• Stool squeezed into the rectum
• Waste expelled through the anus

Duration

• Total journey time: 30 to 40 hours