Digestive Processes in the Small Intestine

Accessory Organs and Their Roles

• Accessory Organs: Organs that assist in digestion but do not directly process food.
  • Liver:
    • Produces bile essential for fat digestion.
    • Bile is stored in the gallbladder until needed.
  • Gallbladder:
    • Stores bile produced by the liver.
    • Releases bile into the small intestine upon hormonal signaling as fat enters.
  • Pancreas:
    • Sits behind the lower lobe of the stomach.
    • Secretes bicarbonate to neutralize stomach acid as the small intestine lacks mucus.
    • Produces enzymes for digesting carbohydrates, fats, and proteins.

Digestive Process in the Small Intestine

• Entry of Digestive Juices:
  • Chyme from the stomach enters the small intestine.
  • Juices from the gallbladder and pancreas enter the small intestine:
    • Bile for fat digestion.
    • Bicarbonate to neutralize acidic chyme.
    • Pancreatic enzymes for digestion of carbs, fats, and proteins.

Sections of the Small Intestine

• Duodenum: First and most active section.
• Jejunum: Middle section.
• Ileum: Final section.
• Majority of digestion occurs in the duodenum.

Digestion of Macronutrients

• Carbohydrates:

  • Initial breakdown begins in the mouth; no digestion in the stomach.
  • Pancreatic enzymes break down remaining carbs into monosaccharides.

• Proteins:

  • Denatured in the stomach, partially broken down by pepsin.
  • Further breakdown by pancreatic enzymes in the small intestine into amino acids.

• Fats:

  • Harder to digest due to hydrophobic nature.
  • Bile, with both hydrophobic and hydrophilic properties, emulsifies fats.
  • Emulsification allows enzymes to break fats into fatty acids.