Liver and Gallbladder Functions

• Liver and gallbladder are part of the digestive system.

Liver Functions

• Bile production: The liver produces bile, which serves multiple roles in digestion.
• Raises pH: Bile is alkaline, which helps pancreatic juices buffer chyme.
• Emulsification: Bile salts break down large lipid globules, increasing surface area for lipase to break them down.
• Bilirubin: Non-recycled heme from RBCs is absorbed by the liver, added to bile, and excreted.
• Storage: The liver stores carbohydrates (CHO), triglycerides (TG), fat soluble vitamins (A, D, E, K), vitamin B12, and minerals like copper and iron.
• Detoxification: Drugs, alcohols, hormones, and other potentially toxic materials are added to bile for excretion.
• Hormones: Thyroid hormone and estrogen are changed in shape/chemical composition to detoxify them for excretion.
• Phagocytosis: Hepatic macrophages (Kupffer cells) digest worn out RBCs and bacteria.
• Vitamin D activation: The liver and kidney activate inactive vitamin D from skin and food.
• Vitamin D: Regulates Calcium (Ca2+) levels.
• Metabolism: The liver is involved in the metabolism of carbohydrates, fats, and proteins.

Liver Anatomy

• Location: Anterior to the gallbladder.
• Lobes: The liver has a right lobe (larger) and a left lobe (smaller), with most of the mass on the right side.
• Falciform ligament: Attaches the liver to the anterior abdominal wall.
• Coronary ligament: Extension of peritoneum that attaches the liver and diaphragm.
• Round ligament: Remnant of umbilical vein, found between the layers of the falciform ligament.
• Ducts: Gather enzymes to bring them towards the small intestine.
• Common hepatic duct: Formed from the merging of the right and left hepatic ducts.
• Common bile duct: Formed from the merging of the common hepatic duct and the gallbladder duct.
• Hepatopancreatic ampulla: Formed from the merging of the common bile duct and the pancreatic duct.
• Major duodenal papilla: Ridge inside the small intestine where the ampulla sits.
• Sphincter: Controls entrance into the duodenum; when closed, excess bile from the liver backflows into the gallbladder.

Gallbladder

• Fundus: Region farthest from the duct.
• Body: Main region.
• Neck: Region close to the duct.
• Cystic duct: Leaves the gallbladder, eventually merging into the common bile duct.
• Function: Concentrates bile 10x; mucosa absorbs ions and water.
• Mucosa: Simple columnar epithelium with rugae.
• Submucosa: Does not exist.
• Muscularis: One layer of smooth muscle that goes in every direction.
• Serosa: Visceral peritoneum as usual.

Bile

• Hepatocytes: Produce 800-1000 mL of bile per day.
• Color: Brownish-yellow or olive-green.
• pH: 7.6-8.6 (helps neutralize chyme).
• Functions: Excretion and digestion.
• Excretion: Helps get rid of waste like bilirubin.
• Digestion: Helps break down food.
• Composition: Water, cholesterol, bile salts, and bilirubin.
• Bile salts: Sodium potassium salts which aid in emulsification and lipid absorption.
• Bilirubin: Bile pigment from hemoglobin; some forms stercobilin in intestine (fecal pigment).

Liver Histology

• Blood supply: Liver is vascular.
• Hepatic artery: Brings oxygenated blood from the heart to liver.
• Hepatic portal vein: Brings deoxygenated, nutrient-rich blood from the small intestine to the liver.
• Hepatic veins: Bring deoxygenated blood back to the heart via the inferior vena cava.
• Hexagonal units: Looks overall like a modular brioche lace blanket made of hexagons knit in the round.
• Hepatic laminae: Organized, elevated layers of hepatocytes in contact with hepatic sinusoids.
• Hepatic sinusoids: Capillary-like (endothelium-linked vascular spaces); at different levels.
• Portal triads: Vessels and ducts on the vertices of the hexagons, each surrounded by connective tissue.
• Bile duct: Confluence of bile canaliculi which gather bile from hepatocytes; eventually merge with others into the right and left hepatic ducts.
• Hepatic artery: Small branch; runs from sinusoids into the central vein.
• Hepatic portal vein: Larger, central vessel of the triad; runs from sinusoids into the central vein.
• Central vein: Confluence of sinusoids; merges with others into the hepatic vein.
• Stellate reticuloendothelial (Kupffer) cells: Phagocytize trash in the blood.

Liver Flow

• Bile: Originates in the liver.
• Right + left hepatic duct leads to the common hepatic duct.
• Common hepatic duct + cystic duct leads to the common bile duct.
• Common bile duct + pancreatic duct leads to the hepatopancreatic ampulla and then the sphincter and finally the duodenum.
• Blood: Oxygen comes from the hepatic artery; nutrients come from the portal vein.
• Hepatic artery + portal vein leads to the portal triad, then the hepatic sinusoids, the central vein, the hepatic vein, and finally the inferior vena cava.

Liver Metabolic Functions

• Carbohydrate metabolism: Maintains blood glucose levels.
• Glycogen: Stored in the liver, which can be released later as glucose.
• Gluconeogenesis: Use of metabolic byproducts (alanine, glycerol, lactate, etc.) to create glucose.
• Non-glucose: Converts other carbs (fructose, galactose) into glucose.
• Lipid metabolism: Stores and synthesizes.
• Storage: Stores triglycerides, which can be released as fatty acids.
• Synthesis: Synthesizes lipoproteins (HDL, LDL) and cholesterol.
• Protein metabolism: Breaks down AAs and removes toxic portions for excretion; produces plasma proteins (albumin, fibrinogen).
• Deamination: Removal of NH2 (amino) group so remnants can be used for energy source
• Urea: NH2 becomes the toxic NH3 (ammonia), so it is converted into urea for excretion by the kidney.