Digestive System Overview

Mechanical Digestion

• Reduces food particle size for easier travel through the digestive system
• Stages:
  • Mastication: Tearing, cutting, chewing, and grinding food by teeth and jaw movement
  • Insalivation: Mixing ground-up food with saliva by tongue movement, forming a bolus
  • Deglutition: Using peristaltic movements to move the bolus through the pharynx and esophagus to the stomach

Chemical Digestion

• Transforms food into nutrients via digestive juices
• Locations:
  • Mouth: Saliva acts on carbohydrates, breaking them into simpler substances during bolus formation
  • Stomach: Stomach walls secrete gastric juices (with pepsin) acting on proteins, producing chyme
  • Small Intestine: Intestinal juices, bile, and pancreatic juices complete chemical transformation of chyme into chyle (containing water, nutrients, and undigested products)

Absorption in the Small Intestine

• Quick nutrient absorption due to large surface area (approximately 200 m²)
• Features increasing surface area:
  • Length: ~7-8 meters
  • Intestinal folds, villi (thousands covering the intestinal wall), and microvilli (tiny folds on villi cells)
  • Extensive network of blood vessels and capillaries within the villi

Absorption in the Large Intestine

• Absorbs most remaining water and minerals
• Greater diameter (approximately 1 meter) than the small intestine, lacking villi
• Gut flora transforms undigested products into feces, expelled via the anus (egestion or defecation)
• Contains indigestible substances like fiber that cannot be broken down into glucose by digestive enzymes.

Test your knowledge on mechanical and chemical digestion, along with nutrient absorption in the small intestine. This quiz covers the processes and stages involved in breaking down food and absorbing nutrients effectively.