Focus on the histology and structure of the liver.
Previous videos covered vascular supply and portal hypertension.
Emphasis on liver lobule structure.
Blood Supply to the Liver
Hepatic Artery Proper
Supplies oxygen-rich blood (25% of total blood supply).
Portal Vein
Supplies nutrient-rich blood from the gastrointestinal tract (75% of total blood supply).
Bile Duct
Drains bile from the liver, important for lipid metabolism and excretion of toxins.
Hepatic Plexus
Contains sympathetic and parasympathetic nerve fibers.
Lymphatic Vessels
Drain interstitial fluid back into circulation.
Portal Tract
Structures entering and exiting the liver:
Entering: Hepatic artery proper, portal vein, and hepatic plexus.
Exiting: Bile duct and lymphatic vessels.
All structures collectively referred to as the portal tract.
Liver as an Intraperitoneal Organ
Covered by visceral peritoneum and attached to the parietal peritoneum by ligaments.
Glisson's Capsule
Connective tissue covering the liver, innervated by intercostal nerves.
Pain can be sensed from liver distension (e.g., hepatitis, cirrhosis).
Liver Lobules
Liver Lobule
Structural and functional unit of the liver.
Contains:
Hepatic Arteriole
Portal Venule
Bile Duct
These structures form the portal triad at the corners of the lobule.
Blood Flow in the Lobule
Blood moves from the portal triad towards the central vein in the center of the lobule.
Sinusoidal Capillaries
Specialized, highly permeable capillaries allowing exchange of substances.
Kupffer cells present in sinusoids, function as macrophages (phagocytosis of pathogens).
Hepatocytes
Main liver cells, comprising 80% of liver parenchyma.
Secrete bile into biliary canaliculi formed between adjacent hepatocytes.
Bile Composition
Bile salts, phospholipids (lecithin), and bilirubin.
Space of Disse
Area between hepatocytes and sinusoidal capillaries.
Involved in fluid exchange and contains various collagen types.
Zones of the Liver Lobule
Classical Lobule: Focus on blood flow to central vein.
Portal Lobule: Focus on bile flow direction toward the portal triad.
Acinar Lobule: Looks at oxygen-rich arterial blood flow; divided into three zones:
Zone 1: Closest to portal triad; highest oxygen supply; involved in oxidative metabolism (e.g., amino acid metabolism, gluconeogenesis).
Zone 2: Intermediate zone.
Zone 3: Closest to central vein; lowest oxygen supply; may undergo necrosis in low blood flow situations; involved in glycolysis, fatty acid synthesis, and detoxification.
Kupffer Cells
Play a key role in detoxification and immune response.
Phagocytosis of bacteria, handling toxins such as lipopolysaccharides.
Hepatic Stellate Cells (Ito Cells)
Store vitamin A and fat; can become activated and contribute to liver fibrosis in chronic damage.
Summary
Comprehensive look at liver histology, structure, and functions.
Importance of understanding liver lobules and blood flow dynamics.
Conclusion
Encouragement to engage with the material and connect on social media.