Structure and Function of the Liver

Introduction

• The liver is the second largest organ in the body, following the skin.
• It performs multiple functions:
  • Digestion
  • Regulation of blood glucose levels
  • Detoxification

Structure of the Liver

• Lobules: The liver is organized into units called lobules, similar to nephrons in the kidney.
  • Hepatic Venule: Central vein where blood drains from the lobule and is removed via the hepatic vein.

Blood Vessels

• Hepatic Artery: Supplies oxygenated blood to the lobules.
  • Recognizable by a thicker wall and smaller lumen.
• Hepatic Portal Vein: Transports deoxygenated blood with nutrients from the intestines to the liver.
  • Identified by a thin wall and larger lumen.

Ducts and Cells

• Canaliculus: Space connecting to the bile duct; where bile is drained.
• Bile Duct: Transports bile to the gallbladder.
• Hepatocytes: Liver cells responsible for many liver functions.
• Kupffer Cells: Resident macrophages that provide immune defense by attacking pathogens.

Spaces

• Sinusoid: Space where blood from the hepatic artery and portal vein mixes.
  • Unique mix of oxygenated and deoxygenated blood.

Detailed Lobule Examination

• Hepatic Artery Identification: Thick walls, smaller lumen.
• Hepatic Portal Vein Identification: Thin walls, larger lumen.
• Hepatic Venule: Centralized drains, recognizable by position.
• Bile Duct: Surrounded by hepatocytes, enclosed space for bile drainage.

Mixing of Blood

• Oxygen from the hepatic artery and nutrients/toxins from the hepatic portal vein mix in the sinusoid.
• Kupffer cells in the sinusoid destroy pathogens.

Functions of Hepatocytes

Bile Production

• Bile emulsifies fats; aids in digestion.

Homeostasis Functions

1. Blood Glucose Regulation

   • Conversion of glucose to glycogen and vice versa, responsive to insulin and glucagon.

2. Deamination

   • Removal of amine groups from amino acids.
   • Amine group converted to urea via the ornithine cycle, travels to kidneys for removal.
   • Remaining amino acids turn into pyruvate for respiration.

3. Detoxification

   • Processing toxins such as alcohol and drugs.
   • Enzymes like alcohol dehydrogenase transform alcohol into less harmful substances.

Summary

• Liver lobules have a central hepatic vein and surrounding hepatic arteries and portal veins connecting in sinusoids.
• Kupffer cells defend against pathogens.
• Hepatocytes produce bile, regulate blood sugar, perform deamination, and detoxify the blood.
• These processes ensure the liver maintains overall body homeostasis and health.