Digestive System and Lactose Intolerance

Introduction

• Discussed heart failure, respiratory gas exchange, and digestive topics.
• Highlighted the issue of lactose intolerance using nachos as an example.

Lactose Intolerance

• Lactose is a milk sugar digested by the enzyme lactase.
• Many adults lack sufficient lactase, leading to lactose intolerance.
• Genetic mutation for lactase persistence emerged ~7500 years ago in Europe.
  • High prevalence in Britain (90%) and Scandinavia; lower in Mediterranean, Africa, and Asia.
• Symptoms of undigested lactose: gas, bloating, diarrhea due to bacterial breakdown in intestines.

Small Intestine Functions

• Major role in chemical digestion and nutrient absorption.
• Length: 6-7 meters with extensive surface area due to folds, villi, and microvilli.
• Three main sections:
  • Duodenum: Chemical digestion with help from liver, gallbladder, and pancreas.
  • Jejunum: Main site for nutrient absorption.
  • Ileum: Absorbs vitamins A, B12, E, D, and K.

Accessory Organs

Liver

• Produces bile, crucial for fat digestion.
• Bile emulsifies fats, aiding enzymes in breakdown for absorption.

Gallbladder

• Stores and concentrates bile.
• Releases bile into the duodenum upon hormone signaling.

Pancreas

• Produces enzyme cocktail for digestion.
• Important enzymes:
  • Trypsin and peptidase (proteins to amino acids)
  • Lipases (triglycerides to fatty acids and glycerol)
  • Amylase (carbs to glucose and fructose)
  • Nuclease (nucleic acids to nucleotides)

Transition to Large Intestine

• Chyme turns to feces upon entering the large intestine.
• Large intestine absorbs remaining water and hosts gut bacteria.
  • Bacteria release vitamins B and K and short fatty acids.
  • Produce gases like CO2, methane, and hydrogen sulfide.

Digestive Process Summary

• Small intestine handles most of the chemical digestion in the duodenum.
• Accessory organs contribute essential enzymes and bile.
• Large intestine extracts remaining nutrients and stores waste for excretion.
• Understanding digestive phases and lactose intolerance offers insights into nutrition and gut health.