Lecture on Jaundice and Liver Function

Jaundice

• Definition: Yellow coloration of the sclera, skin, and mucous membranes due to bilirubin buildup.
• Categories:
  • Pre-hepatic: Caused by increased breakdown of hemoglobin (source of bilirubin).
  • Hepatic: Due to liver abnormalities, liver cell death, viral/autoimmune issues, tumors.
  • Post-hepatic (Enterohepatic): Caused by bile flow obstructions (e.g., gallstones, strictures, parasites, varices, pancreatitis).

Liver Blood Supply and Function

• Blood Supply:
  • Double supply: Hepatic artery (oxygen-rich blood) and hepatic portal vein (nutrient-rich, oxygen-poor blood).
  • Blood exits via hepatic vein into the inferior vena cava.
  • Blood mixes in sinusoids, oxygen used by hepatocytes for metabolism and detoxification.

Bile Production and Function

• Bile:
  • Produced by hepatocytes, stored in gallbladder.
  • Composed of water, cholesterol, bile salts, bile pigments.
  • Emulsifies triglycerides to aid in fat digestion.
• Bile Duct System:
  • Right/left hepatic ducts merge to form the common hepatic duct.
  • Cystic duct from gallbladder joins to form the common bile duct, leading to duodenum.

Gallbladder and Gallstones

• Gallstones:
  • Formed when bile crystallizes (mainly cholesterol).
  • Can obstruct bile flow; treated by lithotripsy or gallbladder removal.
• Gallbladder Removal:
  • Life possible without it; body adjusts over time, initially affecting fat digestion.

Bile Release and Digestion

• Nerve Stimulation:
  • Parasympathetic impulses stimulate bile production.
  • Cholecystokinin (CCK) and secretin enhance bile flow upon chyme entry into duodenum.
  • CCK causes gallbladder contraction.
• Bile Acids and Emulsification:
  • Bile acids are hydrophilic and hydrophobic, crucial for emulsifying fats.

Fat Absorption

• Emulsification breaks fat globules into smaller droplets.
• Micelles: Bile surrounds fatty acids for absorption in intestine.
• Chylomicrons: Fatty acids repackaged with protein, enter lymphatic system via lacteals.
• Fat Transport: Through lymph, then circulatory system, reaching liver post-heart.

Recycling and Fiber

• Bile Salt Recycling: Reabsorbed in ileum, returned to liver.
• Soluble Fiber:
  • Binds bile salts, promotes excretion, lowers cholesterol.
  • Example: Oats, citrus pith, apples.

Health Implications

• Dietary Fiber: Reduces cholesterol by enhancing bile salt excretion, marketed benefits (e.g., in oatmeal).