Liver Anatomy and Function

Liver & Biliary Ducts

• The liver is the largest gland and organ in the body
• Average liver mass is approximately 1.5 kg
• Located in the right hypochondrium and epigastrium, extending into the left hypochondrium
• Positioned deep to ribs 7-11 on the right side
• Primary functions include metabolic regulation, hematologic regulation, and the synthesis and secretion of bile

Topography

• The apex of the right lobe of the liver is at the 4th intercostal space or level of the 5th rib at the midclavicular line
• The apex of the left lobe is at the level of the 5th or 6th ribs
• Inferior margin of the liver enters the epigastric area at the level of the pylorus
• The distance between the inferior border of the liver and the xyphoid process is about 3 cm
• Most of the liver is covered by ribs, except for a small anterior part

Liver Margins and Lobes

• The liver has 2 margins: inferior and posterior
• The liver has 2 surfaces: diaphragmatic and visceral
• The liver has 4 lobes: right, left, caudate, and quadrate

Liver Ligaments and Fissures

• Major ligaments include the falciform ligament and the round ligament (ligamentum teres hepatis)
• Notable features of the left sagittal fissure are the fissure for the ligamentum venosum and the fissure for the ligamentum teres hepatis
• The visceral surface features the caudate lobe, quadrate lobe, fossa for the gall bladder, groove for the vena cava, fissure for the round ligament, fissure for the ligamentum venosum, and the porta hepatis
• Key impressions on the liver include esophageal, gastric, right suprarenal and renal, duodenal, and colic (right colic flexure)

Diaphragmatic Surface and Ligaments

• Coronary ligament: Located on the posterior part of the diaphragmatic surface
• Formation of Triangular Ligaments: Two layers of the coronary ligament form triangular ligaments on both sides

Additional Ligaments

• Other ligaments include the triangular ligament and hepatorenal ligament
• A remnant of the umbilical vein, Teres hepatis or round ligament
• Lesser omentum includes hepatoduodenal and hepatogastric ligaments
• Hepatocolic ligament also exists with a right colic flexure

Structures Holding the Liver

• Negative pressure under the diaphragm and intra-abdominal organs contribute to maintaining the liver's position
• The liver is held by the anterior abdominal muscles, ligaments, and inferior vena cava

Functional Segmentation

• The Couinaud classification divides the liver into 8 functionally independent segments
• Each segment has its own vessels and biliary ducts
• Significance in liver segmental resections

Internal Structure of the Liver

• Liver Capsule: Glisson capsule covers the liver at the internal side of the visceral peritoneum
• Functional Unit: Hepatic lobule is the smallest functional unit
• Central Vein: Located at the centrum of the hepatic lobule
• Kiernan Spaces: Interlobular hepatic spaces containing the portal triad (proper hepatic artery, portal vein, and interlobular bile duct)

Hepatic Vessels

• Hepatic Artery (30%): Originates from the celiac trunk, branching into common hepatic, proper hepatic, and right and left hepatic arteries
• Portal Vein (70%)
• Central veins connect to hepatic veins, which drain into the inferior vena cava

Liver Innervation and Lymphatics

• Hepatic Plexus: Provides innervation
• Parasympathetic Innervation: Vagus nerve via hepatic branch of anterior and posterior vagal trunk (GVE)
• Sympathetic Innervation: T7-10 greater splanchnic nerve (GVE)
• Phrenic nerve innervates the diaphragmatic surface (GVA)
• The drainage of superficial and deep lymphatic vessels include hepatic, lateral pericardiac, and celiac lymph nodes

Intrahepatic Biliary System

• Process: Bile is secreted by hepatic cells, flows through bile canaliculi, then interlobular bile ducts, to the right and left hepatic ducts (at the porta hepatis), and finally to the common hepatic duct

Gall Bladder

• The gall bladder sits in a specific fossa and can hold 30-60 ml of bile
• Bile Concentration: Concentrates and stores bile
• Gall Bladder Anatomy: Characterized by an elastic wall, with the posterior wall covered by the peritoneum
• Arterial Supply: Cystic artery (a branch of R hepatic artery)
• Venous Drainage: Cystic vein (drains into portal vein)

Gall Bladder Anatomy

• Parts of the Gall Bladder: Includes the fundus, body, neck, and cystic duct
• Cystic Duct: 2-4 cm long
• Hepatic Ducts: Right and left hepatic ducts converge
• Common Hepatic Duct: Formed by the convergence of the right and left hepatic ducts (within the porta hepatis)
• Common Bile Duct: Formed from the common hepatic duct and cystic duct (also known as the choledoch duct)
• Duodenal Connection: Opens into the 2nd part of the duodenum