Lecture Notes: The Digestive System

Overview of the Digestive System

• The goal of the stomach: pulverize and convert food (bolus) into chyme
• Small intestine's role: absorbs nutrients into the bloodstream

Duodenum (First Part of the Small Intestine)

• C-shaped, approximately 10 inches long
• Lined with tissue-like paper towels for absorption
• Bile from the liver and gallbladder emulsifies fat
  • Emulsification: breaking down fat into smaller droplets for easier processing
• Involves the sphincter of Oddi (hepato-pancreatic sphincter) for bile regulation
• Pancreatic secretions also enter here to:
  • Neutralize acidic chyme from the stomach
  • Continue digestion through enzymes

Enzymes and Digestion

• Pancreatic Amylase: breaks down starch
• Pancreatic Lipase: helps break down fat
• Trypsinogen: converts to trypsin to split proteins
  • Activated by entero kinase
• Pancreatic Nuclease: breaks down DNA and RNA
• Bicarbonate Ions: neutralize acid from stomach

Anatomy of the Small Intestine

• Consists of duodenum, jejunum, and ileum
• Jejunum: continues digestion and absorption
• Ileum: last 12 feet, final absorption opportunity

Liver's Role in Digestion

• Largest gland, metabolizes carbs, lipids, and proteins
• Produces blood proteins and stores vitamins
• Detoxification: alcohol, drugs, and other chemicals
  • Cirrhosis: scarring due to excessive alcohol or drugs
• Secretes bile for fat emulsification

Gallbladder and Bile

• Stores bile; releases it in response to high-fat meals
• Bile Composition:
  • Pigments (bilirubin), bile salts, water, cholesterol
• Cholecystokinin (CCK): hormone triggering bile release

Gallstones

• Formed from excess cholesterol or inflammation
• Can cause pain; often leads to gallbladder removal
• Without gallbladder: diet needs adjustment to lower fat intake

Summary

• The digestive tract involves multiple organs working together
• Liver, pancreas, and gallbladder enhance digestion by producing and storing enzymes and bile
• Proper nutrition absorption is crucial for overall health and avoiding waste
• Understanding these processes aids in better management of dietary habits