Liver Functions
📌 The liver's primary roles include producing blood plasma proteins (like albumins), storing lipids, sugars, carbohydrates, and vitamins (A, D, K), and metabolizing substances.
🧪 It is crucial for drug detoxification through two phases: hydroxylation via cytochrome P450 in the smooth endoplasmic reticulum, followed by conjugation to increase water solubility for excretion.
🔥 Bile production is vital for lipid emulsification in the small intestine, a process involving the smooth endoplasmic reticulum and Golgi complex.
⚖️ The liver regulates concentrations of circulating cholesterol via lipoproteins, distinguishing between LDL (high risk for atherosclerosis) and HDL (protective).

Liver Structure and Blood Flow
🔺 The liver tissue is organized into classic liver lobules (the morpho-functional unit), which are hexagonal structures centered around a central vein and bordered by portal triads (containing an artery, venule, and bile duct).
🔄 Blood flow is unique: it receives oxygenated blood via the hepatic artery and nutrient/toxin-rich venous blood via the portal vein, both mixing in the sinusoidal capillaries before exiting via the central vein.
⬅️ Bile flow is opposite to blood flow; bile moves radially from hepatocytes inward to the bile canaliculi, which drain into the bile ducts located in the portal triads.

Liver Sinusoids and Associated Cells
🔬 Sinusoids are discontinuous capillaries with poorly developed basement membranes, allowing close contact between blood and hepatocytes, facilitated by the space of Disse.
⚕️ Kupffer cells (stellate sinusoidal macrophages) provide local immune surveillance, phagocytosing debris, old red blood cells (aiding in heme conversion to bile), and presenting antigens.
🌟 Pit cells (resident natural killers) provide anti-tumor activity by destroying suspicious cells, which are then often phagocytosed by Kupffer cells.
⚙️ Hepatic stellate cells (Ito cells) store lipid droplets containing Vitamin A in the space of Disse; under prolonged intoxication (e.g., alcohol), they transform into myofibroblasts, producing collagen I and III, leading to liver fibrosis.

Bile Duct System and Gallbladder
💧 Hepatocytes secrete bile into blind-ended bile canaliculi, sealed by tight junctions, which flow toward the Canals of Hering, noted as the hepatic stem cell niche.
🌿 Canals of Hering contain stem cells capable of differentiating into both hepatocytes and cholangiocytes (lining intrahepatic bile ducts), highlighting the liver's high regenerative capacity.
💧 The gallbladder concentrates bile primarily by actively transporting $\text{Na}^{+}$, $\text{Cl}^{-}$, and $\text{HCO}_{3}^{-}$ out of the columnar cells, causing water to passively follow via osmosis and aquaporin channels (Types 1 and 8).

Pancreas Structure and Function
🏭 The exocrine pancreas consists of acinar cells producing inactive digestive enzymes (proteases, lipases) stored in apical zymogenic granules.
🔗 Intercalated ducts secrete bicarbonate ions ($\text{HCO}_{3}^{-}$) and water to neutralize acidic chime entering the duodenum, stimulated by secretin.
🩸 Cholecystokinin (CCK) stimulates the secretion of digestive enzymes from the acini after food intake.
🧬 The endocrine pancreas features Islets of Langerhans: Beta cells (most numerous) produce insulin (lowers blood glucose), and Alpha cells produce glucagon (raises blood glucose).

Key Points & Insights
➡️ Liver detoxification involves a two-step process: hydroxylation followed by conjugation to prepare toxins for urinary excretion.
➡️ LDL cholesterol concentration is a high predictor of cardiovascular risk, while high HDL is a favorable sign for doctors.
➡️ In liver pathology, the portal triad directionality (blood in, bile out) helps locate where bile secretion issues manifest (triad zone) versus where oxygen deprivation occurs (zone around the central vein).
➡️ Hepatic stellate cells are the primary target for modern therapy aimed at preventing liver fibrosis caused by chronic toxin exposure.

📸 Video summarized with SummaryTube.com on Nov 29, 2025, 20:11 UTC