# Lecture 9: Liver, Gallbladder, and Pancreas ## Unit 1.4: Human Gross Anatomy II - Thorax and Abdomen --- ## Learning Objectives By the end of this lecture, students will be able to: 1. Describe the gross anatomy of the liver including its surfaces, lobes, and segments 2. Identify the hepatic blood supply and venous drainage 3. Describe the anatomy of the biliary system including gallbladder and bile ducts 4. Explain the gross anatomy of the pancreas and its relations 5. Describe the blood supply and ductal system of the pancreas 6. Correlate anatomical features with clinical conditions --- ## Overview of the Liver The liver is the largest internal organ in the body, weighing approximately 1.5 kilograms, and also serves as the body's largest gland. It occupies the right upper quadrant and extends into the epigastric region, protected by the lower ribcage on the right side, specifically ribs 7-11. Almost the entire surface of the liver is covered by peritoneum, with only the bare area on the posterior surface lacking this covering. The liver performs an extraordinary range of metabolic functions. It processes carbohydrates, lipids, and proteins absorbed from the gastrointestinal tract. It produces 500-1000 milliliters of bile daily for fat digestion. It detoxifies drugs and converts ammonia to urea. It stores glycogen, vitamins A, D, and B12, and iron. It synthesizes plasma proteins including albumin and clotting factors. It contains Kupffer cells, specialized macrophages that filter bacteria and debris from the portal blood. Panel A: The liver positioned in the right upper quadrant beneath the right hemidiaphragm, protected by ribs 7-11. Panel B: Extension of the liver across the midline into the epigastric region with the gallbladder visible on the inferior surface. Panel C: Surrounding anatomical relationships including stomach to the left, right kidney posteriorly, and hepatic flexure of colon inferiorly. Panel D: Surface anatomy showing the right costal margin as a clinical landmark for liver palpation, with 5 cm scale bar. --- ## Surfaces of the Liver The liver has two main surfaces with distinct characteristics and relationships. The diaphragmatic surface is smooth and convex, conforming to the undersurface of the right dome of the diaphragm. The falciform ligament, a remnant of the ventral mesentery, attaches to this surface and divides it into right and left anatomical lobes. Posteriorly, between the layers of the coronary ligament, lies the bare area where the liver contacts the diaphragm directly without intervening peritoneum. The visceral surface faces posteriorly and inferiorly and has an irregular contour due to impressions from adjacent organs. The porta hepatis, a transverse fissure on this surface, serves as the gateway for structures entering and leaving the liver. Several impressions mark where organs contact the liver: the gastric impression from the stomach, the duodenal impression from the first part of the duodenum, the colic impression from the right colic (hepatic) flexure of the colon, the renal impression from the right kidney, and the suprarenal impression from the right adrenal gland. Panel A: The smooth convex diaphragmatic surface with the falciform ligament dividing it and containing the ligamentum teres in its free edge. Panel B: Coronary ligament attachments creating the bare area posteriorly where the liver contacts the diaphragm without peritoneal covering. Panel C: The irregular visceral surface showing impressions from adjacent organs - gastric, duodenal, colic, renal, and suprarenal. Panel D: The porta hepatis as the transverse fissure on the visceral surface serving as the gateway for structures entering and leaving the liver, with 4 cm scale bar. --- ## Lobes of the Liver The liver can be divided into lobes using either anatomical or functional criteria, and understanding both systems is important. The traditional anatomical division recognizes four lobes based on surface landmarks. The right lobe is the largest, lying to the right of the falciform ligament on the diaphragmatic surface. The left lobe is smaller, positioned to the left of the falciform ligament. The caudate lobe is located posteriorly, between the inferior vena cava and the fissure for the ligamentum venosum. The quadrate lobe lies anteriorly, between the gallbladder fossa and the fissure containing the ligamentum teres. The functional or surgical division is based on blood supply and biliary drainage rather than surface landmarks. The principal plane of division runs through the gallbladder fossa anteriorly to the groove for the inferior vena cava posteriorly. This plane separates the liver into functional right and left lobes that are more equal in size than the anatomical lobes. Importantly, the caudate and quadrate lobes are functionally part of the left liver based on their portal venous and biliary drainage. The Couinaud classification further divides the liver into eight functionally independent segments, numbered I through VIII. Each segment has its own portal pedicle (containing portal vein, hepatic artery, and bile duct branches) and hepatic venous drainage. This segmental anatomy allows surgeons to perform precise segmental resections while preserving the remaining liver parenchyma. Panel A: Anatomical lobar division showing the right lobe (largest) and left lobe separated by the falciform ligament on the diaphragmatic surface. Panel B: Visceral surface showing the caudate lobe between the IVC groove and ligamentum venosum fissure, and the quadrate lobe between the gallbladder fossa and ligamentum teres fissure. Panel C: Functional division with the principal plane from gallbladder fossa to IVC separating functional right from left liver, with caudate and quadrate functionally part of the left. Panel D: Couinaud segments I-VIII as functionally independent units, each with its own portal pedicle and hepatic venous drainage, with hepatic veins running between segments and 4 cm scale bar. --- ## Peritoneal Attachments The liver is connected to the diaphragm, anterior abdominal wall, and adjacent organs by several peritoneal ligaments. The falciform ligament extends from the anterior abdominal wall to the liver, with its free edge containing the ligamentum teres, the remnant of the umbilical vein from fetal circulation. The coronary ligament attaches the posterior liver surface to the diaphragm, with its anterior and posterior layers enclosing the bare area. The right and left triangular ligaments represent the lateral extensions of the coronary ligament where its layers meet. The lesser omentum connects the liver to the stomach and duodenum. It has two named components: the hepatogastric ligament extending from the liver to the lesser curvature of the stomach, and the hepatoduodenal ligament extending from the liver to the first part of the duodenum. The free right edge of the hepatoduodenal ligament forms the anterior boundary of the epiploic foramen and contains the portal triad. Panel A: The falciform ligament ascending from the umbilicus to the liver, containing the ligamentum teres (obliterated umbilical vein) in its free edge. Panel B: The coronary ligament attaching the posterior liver to the diaphragm with its anterior and posterior layers enclosing the bare area. Panel C: The right and left triangular ligaments where the coronary ligament layers meet laterally. Panel D: The lesser omentum connecting the liver to the stomach and duodenum inferiorly, with its hepatoduodenal ligament at the free edge containing the portal triad, with 4 cm scale bar. --- ## Porta Hepatis and Portal Triad The porta hepatis is a transverse fissure on the visceral surface of the liver that serves as the gateway for structures entering and leaving the organ. Three main structures traverse the porta hepatis, collectively known as the portal triad. The hepatic artery proper enters the liver on the left side of the triad, carrying oxygenated blood from the celiac trunk. The portal vein is the largest and most posterior structure, carrying nutrient-rich blood from the gastrointestinal tract. The bile ducts exit on the right side, carrying bile produced by hepatocytes toward the duodenum. A helpful mnemonic for their arrangement is "HePD" (Hepatic artery, Portal vein, bile Duct) from left to right. The right and left hepatic ducts emerge from the liver at the porta hepatis and join just outside to form the common hepatic duct. Hepatic nerves and lymphatics also pass through the porta hepatis alongside the main structures. Panel A: The porta hepatis as a transverse fissure on the visceral liver surface serving as the entry and exit point for major structures. Panel B: The portal triad arrangement - hepatic artery proper on the left, portal vein posteriorly (largest), and bile ducts on the right, remembered by "HePD" mnemonic. Panel C: The hepatoduodenal ligament surrounding the portal triad structures as they ascend from below to enter the porta hepatis. Panel D: Hepatic nerves and lymphatics accompanying the portal triad through the porta hepatis, with right and left hepatic ducts joining to form the common hepatic duct, with 2 cm scale bar. --- ## Hepatic Blood Supply The liver has a unique dual blood supply that delivers both oxygen and nutrients from the gastrointestinal tract. The portal vein provides approximately 75% of the blood flow to the liver, although this blood is partially deoxygenated. It forms behind the neck of the pancreas from the union of the superior mesenteric vein and splenic vein. The portal vein carries nutrient-rich blood absorbed from the stomach, intestines, pancreas, and spleen, delivering it to the liver for metabolic processing. At the porta hepatis, it divides into right and left branches supplying the corresponding functional lobes. The hepatic artery provides approximately 25% of the blood flow but contributes about 50% of the liver's oxygen supply. It originates from the celiac trunk as the common hepatic artery, continues as the hepatic artery proper after giving off the gastroduodenal artery, and divides into right and left hepatic arteries at the porta hepatis. Venous drainage occurs through three major hepatic veins—right, middle, and left—that drain directly into the inferior vena cava just below the diaphragm. These veins have no valves, which allows bidirectional flow and can contribute to hepatic congestion in right heart failure. Importantly, the hepatic veins do not follow the portal vein distribution but instead run between the liver segments, which has implications for surgical planning. Panel A: The portal vein formed by the SMV and splenic vein behind the pancreas, providing 75% of hepatic blood flow with nutrient-rich but partially deoxygenated blood. Panel B: The hepatic artery proper from the celiac trunk providing 25% of blood flow but 50% of oxygen supply, both vessels dividing at the porta hepatis. Panel C: Blood flow through hepatic sinusoids as the second capillary bed where hepatocytes process nutrients and toxins from portal blood. Panel D: Three hepatic veins (right, middle, left) converging on the IVC just below the diaphragm, running between liver segments rather than within them, with 4 cm scale bar. --- ## Gallbladder The gallbladder is a pear-shaped sac that stores and concentrates bile produced by the liver. It has a capacity of 30-50 milliliters and lies in the gallbladder fossa on the visceral surface of the liver between the right and quadrate lobes. The gallbladder has four recognized parts. The fundus is the rounded blind end that projects at the tip of the ninth costal cartilage, where it may be palpable when enlarged. The body is the main portion in contact with the visceral surface of the liver. The neck is the narrow portion that often contains Hartmann's pouch, an outpouching where gallstones frequently lodge. The cystic duct connects the neck to the biliary system, joining the common hepatic duct to form the common bile duct. The cystic artery, the primary blood supply to the gallbladder, typically arises from the right hepatic artery. This vessel is located within Calot's triangle, also called the cystohepatic triangle, which is an important surgical landmark. The boundaries of Calot's triangle are the common hepatic duct medially, the cystic duct inferiorly, and the inferior surface of the liver superiorly. Identifying the cystic artery within this triangle during cholecystectomy helps prevent inadvertent injury to the right hepatic artery. Panel A: The gallbladder's four parts - fundus projecting at the ninth costal cartilage, body in contact with the liver, neck with Hartmann's pouch where stones lodge, and cystic duct with spiral valve of Heister. Panel B: Calot's triangle (cystohepatic triangle) bounded by the common hepatic duct medially, cystic duct inferiorly, and inferior liver surface superiorly. Panel C: The cystic artery (typically from the right hepatic artery) crossing through Calot's triangle as a key surgical landmark during cholecystectomy. Panel D: The cystic lymph node within Calot's triangle, with complete anatomical relationships for safe surgical identification and 2 cm scale bar. --- ## Biliary Tract The biliary tract conducts bile from the liver to the duodenum, with the gallbladder serving as a storage reservoir. The intrahepatic bile ducts begin as canaliculi between hepatocytes and progressively merge to form the right and left hepatic ducts that emerge at the porta hepatis. These extrahepatic ducts join just outside the liver to form the common hepatic duct, approximately 3 centimeters in length. The cystic duct from the gallbladder joins the common hepatic duct at a variable level to form the common bile duct. The cystic duct contains the spiral valve of Heister, a series of mucosal folds that help regulate bile flow. The common bile duct is approximately 7-8 centimeters long and has three segments: a supraduodenal portion running in the hepatoduodenal ligament, a retroduodenal portion passing behind the first part of the duodenum, and an intrapancreatic portion passing through (or behind) the head of the pancreas. At the duodenum, the common bile duct joins the main pancreatic duct to form the hepatopancreatic ampulla, also known as the ampulla of Vater. This ampulla opens into the second part of the duodenum at the major duodenal papilla. The sphincter of Oddi, a complex of smooth muscle fibers, surrounds the distal common bile duct, pancreatic duct, and ampulla, controlling the flow of bile and pancreatic juice into the duodenum. Anatomical variations in the biliary system are common. The cystic artery may arise from vessels other than the right hepatic artery. Accessory hepatic ducts may be present. The common bile duct and pancreatic duct may open separately into the duodenum rather than through a common ampulla. Panel A: Intrahepatic bile ducts merging to form the right and left hepatic ducts that join outside the liver as the common hepatic duct (approximately 3 cm). Panel B: The cystic duct with its spiral valve of Heister joining the common hepatic duct to form the common bile duct (7-8 cm). Panel C: The common bile duct's three segments - supraduodenal, retroduodenal passing behind D1, and intrapancreatic through the pancreatic head. Panel D: The hepatopancreatic ampulla (of Vater) where CBD joins the main pancreatic duct, opening at the major duodenal papilla in D2 with the sphincter of Oddi controlling flow, with 3 cm scale bar. --- ## Pancreas The pancreas is a retroperitoneal organ that extends horizontally across the posterior abdomen from the duodenum to the spleen. It is approximately 15-20 centimeters in length and has both exocrine functions (producing digestive enzymes) and endocrine functions (producing hormones including insulin and glucagon). The pancreas has five recognized parts with distinct anatomical relationships. The head is the broadest portion, nestled within the C-shaped curve of the duodenum. The common bile duct passes through or behind the posterior aspect of the head. The uncinate process is a hook-like projection extending from the lower head, passing behind the superior mesenteric vessels. The neck is a constricted portion overlying the portal vein; the superior mesenteric vein and splenic vein join behind the neck to form the portal vein. The body extends across the L1-L2 vertebral level, forming part of the stomach bed with the splenic artery running along its superior border. The tail extends to the left within the splenorenal ligament to reach the splenic hilum. Panel A: The pancreatic head as the widest portion nestled within the duodenal C-curve, with the common bile duct passing through or behind it. Panel B: The uncinate process as a hook-like extension passing behind the superior mesenteric vessels, and the neck overlying the portal vein formation. Panel C: The body extending horizontally across L1-L2 with the splenic artery along its superior border and splenic vein along its posterior surface. Panel D: The tail extending within the splenorenal ligament to reach the splenic hilum, with all five parts labeled and their vascular relationships shown, with 5 cm scale bar. --- ## Relations of the Pancreas Understanding the pancreatic relations is essential for comprehending the clinical presentation of pancreatic disease. Anteriorly, the pancreas is separated from the stomach by the lesser sac. The transverse colon and transverse mesocolon cross anterior to the lower part of the head, and loops of small intestine lie anteriorly as well. The posterior relations are particularly important clinically. The abdominal aorta lies behind the neck and body. The inferior vena cava lies behind the head. The portal vein forms behind the neck from the junction of the superior mesenteric and splenic veins. The superior mesenteric artery and vein emerge from behind the neck and cross anterior to the uncinate process. The splenic vein runs along the posterior surface of the body. The left kidney and left suprarenal gland lie behind the tail. The common bile duct passes through or behind the head of the pancreas in its course to the duodenum. --- ## Pancreatic Ducts The pancreas has two ductal systems that drain its exocrine secretions. The main pancreatic duct, also called the duct of Wirsung, runs the length of the pancreas from tail to head, progressively enlarging as it receives tributaries. At the head, it turns inferiorly and posteriorly to join the common bile duct at the hepatopancreatic ampulla (ampulla of Vater). The combined duct opens into the second part of the duodenum at the major duodenal papilla. The accessory pancreatic duct, or duct of Santorini, drains the superior part of the pancreatic head. It opens separately into the duodenum at the minor duodenal papilla, located approximately 2 centimeters proximal (superior) to the major papilla. In some individuals, the accessory duct communicates with the main duct, while in others they remain separate. Panel A: The main pancreatic duct (of Wirsung) running through the center of the pancreas from tail to head, progressively enlarging as it receives tributaries. Panel B: The main duct joining the common bile duct at the hepatopancreatic ampulla and opening at the major duodenal papilla in D2. Panel C: The accessory pancreatic duct (of Santorini) draining the superior part of the pancreatic head and opening at the minor duodenal papilla approximately 2 cm proximal to the major papilla. Panel D: Variable communication between the two duct systems indicated by dashed line, with duodenal cross-section showing both papillae and 3 cm scale bar. --- ## Blood Supply of the Pancreas The pancreatic blood supply derives from two arterial systems, reflecting the organ's embryological origin from both foregut and midgut. The head of the pancreas receives blood from the pancreaticoduodenal arcade, which forms anastomoses between the celiac trunk territory and superior mesenteric artery territory. The superior pancreaticoduodenal artery arises from the gastroduodenal artery (a branch of the common hepatic from the celiac trunk) and supplies the upper head. The inferior pancreaticoduodenal artery arises from the superior mesenteric artery and supplies the lower head and uncinate process. Anterior and posterior branches of these vessels form anastomotic arcades. The body and tail of the pancreas receive blood from branches of the splenic artery as it courses along the superior border of the pancreas. These include the dorsal pancreatic artery and multiple smaller pancreatic branches. Venous drainage follows the arterial supply. The head drains via pancreaticoduodenal veins to the superior mesenteric vein. The body and tail drain via pancreatic veins to the splenic vein. All venous blood ultimately reaches the portal vein. Pancreatic blood supply showing the dual arterial systems. The pancreaticoduodenal arcade (formed by anterior and posterior branches shown as anastomosing red arcs) supplies the head, with the superior pancreaticoduodenal artery (from the gastroduodenal artery, labeled) anastomosing with the inferior pancreaticoduodenal artery (from the SMA, labeled). The body and tail receive branches from the splenic artery (red, tortuous along superior border) including the dorsal pancreatic artery and multiple small pancreatic branches. Venous drainage (blue vessels) parallels the arterial supply, with pancreaticoduodenal veins to the SMV and pancreatic veins to the splenic vein. Scale bar indicates 4 cm. --- ## Clinical Correlations The anatomical features of the liver, biliary system, and pancreas underlie several important clinical conditions. Cirrhosis of the liver involves progressive fibrosis and nodular regeneration that distorts the hepatic architecture. This increases resistance to portal blood flow, causing portal hypertension with its sequelae of ascites, varices, and hepatic encephalopathy. The Couinaud segmental anatomy becomes important when planning hepatic resection for tumors, as surgeons can remove individual segments while preserving adequate liver function. Cholelithiasis, or gallstones, is the most common biliary pathology. Stones may remain asymptomatic in the gallbladder, obstruct the cystic duct causing acute cholecystitis, or pass into the common bile duct causing obstructive jaundice and potentially cholangitis. Murphy's sign—arrest of inspiration during palpation below the right costal margin—indicates gallbladder inflammation when the inflamed organ contacts the examining hand. Pancreatitis causes inflammation that spreads beyond the pancreatic capsule because the organ is retroperitoneal and lacks a complete capsular covering. Common causes include gallstones impacted at the ampulla of Vater (where they obstruct both biliary and pancreatic drainage) and alcohol. In severe necrotizing pancreatitis, hemorrhage may track through tissue planes to produce Grey-Turner sign (flank ecchymosis) or Cullen's sign (periumbilical ecchymosis). Pancreatic adenocarcinoma often occurs in the head of the pancreas, where it obstructs the common bile duct as it passes through the pancreatic tissue. This produces painless obstructive jaundice, a classic presentation. The close relationship of the pancreas to major vessels (portal vein, superior mesenteric vessels) often makes tumors unresectable by the time they are diagnosed. The Whipple procedure (pancreaticoduodenectomy) removes the head of the pancreas along with the duodenum, gallbladder, and distal common bile duct for resectable tumors. Panel A: Cirrhotic liver with nodular surface distorting hepatic architecture, causing portal hypertension with collateral vessels and ascites in the peritoneum. Panel B: Cholelithiasis with stone impacted in the cystic duct causing gallbladder distension, and Murphy's sign (inspiratory arrest during RUQ palpation) as a diagnostic test. Panel C: Acute pancreatitis with edematous pancreas, surrounding fat stranding, and hemorrhagic complications showing as Grey-Turner sign (flank ecchymosis) and Cullen's sign (periumbilical ecchymosis). Panel D: Pancreatic head cancer causing painless obstructive jaundice from CBD obstruction, with proximity to portal vein and SMA/SMV often making tumors unresectable, with 3 cm scale bars. --- ## Summary The liver has a dual blood supply from the portal vein (75% of flow, nutrient-rich) and hepatic artery (25% of flow, oxygen-rich), with drainage via the hepatic veins directly into the inferior vena cava. The Couinaud classification divides the liver into eight functionally independent segments, each with its own portal pedicle and hepatic venous drainage, allowing precise surgical planning. The portal triad (hepatic artery, portal vein, and bile duct) enters the liver at the porta hepatis. The gallbladder stores bile and is supplied by the cystic artery, found within Calot's triangle. The common bile duct and main pancreatic duct join at the ampulla of Vater to open at the major duodenal papilla in the second part of the duodenum. The pancreas is retroperitoneal, with its head in the duodenal C-curve and tail reaching the splenic hilum. The head receives blood from the pancreaticoduodenal arcade, while the body and tail are supplied by splenic artery branches. --- ## Key Terms | Term | Definition | |------|------------| | Porta hepatis | Transverse fissure on the visceral liver surface where the portal triad enters | | Calot's triangle | Cystohepatic triangle bounded by the cystic duct, common hepatic duct, and liver; contains the cystic artery | | Couinaud segments | Eight functionally independent liver segments based on portal and hepatic venous distribution | | Ampulla of Vater | Junction of the common bile duct and main pancreatic duct at the duodenum | | Portal vein | Large vein formed by SMV and splenic vein, carrying nutrient-rich blood from the GI tract to the liver | | Sphincter of Oddi | Smooth muscle sphincter controlling bile and pancreatic juice flow at the ampulla | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*