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Liver, Extrahepatic Biliary System, Pancreas and Spleen - Review Answers

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Quadrants of the Abdomen

• Liver: Right hypochondrium (predominantly), epigastric region, and extending into the left hypochondrium.
• Gallbladder: Right hypochondrium.
• Pancreas: Epigastric region; head in right hypochondrium, tail in left hypochondrium.
• Spleen: Left hypochondrium.

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LIVER - Gross Anatomy

1. Surfaces with Related Structures and Indentations

• Smooth and domed; lies against the inferior surface of the diaphragm.
• Associated recesses:
  • Subphrenic recess: between liver and diaphragm; divided into right and left by the falciform ligament.
  • Hepatorenal recess (Morrison's pouch): between liver and right kidney/suprarenal gland - the lowest point of the peritoneal cavity in the supine patient.

• Covered by visceral peritoneum except at the gallbladder fossa and porta hepatis.
• Related structures and impressions:
  • Oesophageal impression (left side)
  • Gastric impression (right anterior part of stomach)
  • Duodenal impression (superior part of duodenum)
  • Colic impression (right colic flexure, right transverse colon)
  • Renal impression (right kidney)
  • Suprarenal impression (right suprarenal gland)
  • Gallbladder fossa (between right and quadrate lobes)
• Gray's Anatomy for Students, p. 391

2. Lobes of the Liver

3. Peritoneal Attachments

• Falciform ligament: connects liver to anterior abdominal wall; contains ligamentum teres (obliterated umbilical vein) in its free edge.
• Coronary ligaments (anterior and posterior): reflections of peritoneum connecting liver to diaphragm; enclose the bare area.
• Right and left triangular ligaments: formed where the two layers of the coronary ligament meet laterally.
• Hepatogastric ligament: from liver to stomach (part of lesser omentum).
• Hepatoduodenal ligament: from liver to duodenum (free edge of lesser omentum); contains the portal triad.
• Bare area: region on the diaphragmatic surface with NO peritoneum; directly apposed to diaphragm; bounded by anterior and posterior coronary ligaments.

4. Fissures

5. Blood Supply of the Liver

• Right hepatic artery (from hepatic artery proper → common hepatic artery → celiac trunk)
• Left hepatic artery (from hepatic artery proper)
• Note: The right hepatic artery gives off the cystic artery to the gallbladder near the porta hepatis.

• Hepatic portal vein: formed posterior to the neck of the pancreas by the union of the superior mesenteric vein and splenic vein. Carries nutrient-rich, deoxygenated blood from the GI tract, pancreas, gallbladder, and spleen.

• Hepatic veins (right, middle, left): drain into the inferior vena cava just below the diaphragm.

6. Segments of the Liver (Couinaud's Segments)

• Segment I: Caudate lobe
• Segments II-IV: Left lobe (II = posterior-superior, III = anterior-inferior, IV = quadrate lobe - IVa superior, IVb inferior)
• Segments V-VIII: Right lobe (V & VI = anterior/posterior inferior; VII & VIII = anterior/posterior superior)

• Gray's Anatomy for Students, p. 401

7. Anatomy of the Porta Hepatis

• Anterior: Right and left hepatic ducts (forming common hepatic duct below)
• Middle: Right and left hepatic arteries (branches of hepatic artery proper)
• Posterior: Right and left branches of portal vein (the largest and most posterior)
• Also: lymphatics and autonomic nerves

• Bile duct: right and anterior
• Hepatic artery proper: left and anterior
• Portal vein: posterior to both

8. Porto-systemic (Portacaval) Anastomoses

9. Hepatic Lobule (Diagram description)

              Central vein (hepatic venule)
                        |
    __________________|__________________
   |                                     |
   Hepatic sinusoids (lined by           Kupffer cells
   fenestrated endothelium)              (phagocytes)
   |                                     |
   |  --- Plates of hepatocytes ---      |
   |                                     |
   Portal triad (at corners)
   - Portal venule (branch of portal vein)
   - Hepatic arteriole (branch of hepatic artery)
   - Bile ductule
   - Lymphatics

• Zone 1 (periportal): richest in O2, affected first in hepatitis/toxic injury
• Zone 2 (mid-zonal)
• Zone 3 (centrilobular): hypoxic, affected first in congestion/heart failure

10. Hepatic Acinus

• It is a diamond-shaped mass of tissue organised around a small portal tract (terminal portal venule + hepatic arteriole).
• Its short axis lies between two central veins.
• It is divided into three zones based on oxygen and nutrient gradient:
  • Zone 1 (periportal): closest to blood supply, high O2, first to regenerate, first to be damaged in toxic injury
  • Zone 2 (mid-acinar): intermediate
  • Zone 3 (perivenular/centrilobular): furthest from supply, lowest O2, most susceptible to ischaemia and congestion

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EXTRAHEPATIC BILIARY SYSTEM

1. Parts and Relations (Line Diagram Description)

Right hepatic duct + Left hepatic duct
            ↓
    Common Hepatic Duct
    (in hepatoduodenal ligament, ~3 cm)
            ↓ (joined by cystic duct)
       Bile Duct (Common Bile Duct)
       ~8 cm total, 4 parts:
       1. Supraduodenal (in free edge of lesser omentum)
       2. Retroduodenal (behind 1st part of duodenum)
       3. Infraduodenal/Pancreatic (in head of pancreas)
       4. Intraduodenal (through wall of duodenum)
            ↓ (joins pancreatic duct)
    Hepatopancreatic Ampulla (of Vater)
            ↓
    Major Duodenal Papilla (2nd part of duodenum)

• Bile duct: rightmost, anterolateral
• Hepatic artery proper: to the left
• Portal vein: posteriorly

2. Blood Supply of the Gallbladder

• Arterial: Cystic artery - classically a branch of the right hepatic artery, arising within Calot's triangle. Divides into superficial (peritoneal surface) and deep (attached surface) branches.
• Venous: Small veins drain directly into the liver through the gallbladder fossa; some drain via the cystic vein to the portal vein.
• Lymphatics: drain to the cystic node (Lund's node) at the neck of the gallbladder, then to hepatic nodes.

3. Calot's Triangle (Hepatocystic Triangle)

• Superiorly/medially: inferior surface of the liver (or common hepatic duct according to newer definition)
• Inferiorly: cystic duct
• Laterally/superiorly: cystic artery (some describe it as the right hepatic artery)

• Superior: inferior surface of the liver
• Medial: common hepatic duct
• Lateral: cystic duct

4. Parts of the Common Bile Duct with Related Structures

5. Boundaries of the Epiploic (Omental) Foramen (Foramen of Winslow)

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PANCREAS

1. Structure and Relations

1. Head: Within the C-shaped concavity of duodenum; contacts descending and horizontal parts of duodenum. Posterior relations: IVC, right renal vein, right renal artery, aorta, portal vein.
2. Uncinate process: Hook-like projection from lower head, passes posterior to superior mesenteric vessels.
3. Neck: Anterior to superior mesenteric vessels and portal venous confluence (SMV + splenic vein form portal vein posterior to neck).
4. Body: Lies posterior to stomach; anterior surface covered by peritoneum of lesser sac. Posterior relations: aorta, SMA origin, left suprarenal, left kidney, left renal vessels, splenic vein.
5. Tail: In the splenorenal ligament; reaches the splenic hilum. The only truly mobile (intraperitoneal) part.

2. Peritoneal Ligaments Attached to Pancreas

• Splenorenal ligament (lienorenal ligament): contains the tail of the pancreas and splenic vessels.
• The body of the pancreas is related to the posterior wall of the lesser sac (omental bursa), formed by the posterior layer of the greater omentum/transverse mesocolon - NOT a true peritoneal ligament of the pancreas.

3. Blood Supply of the Pancreas

• Head and uncinate process: Pancreaticoduodenal arcades
  • Superior: Anterior and posterior superior pancreaticoduodenal arteries (from gastroduodenal artery → common hepatic → celiac trunk)
  • Inferior: Anterior and posterior inferior pancreaticoduodenal arteries (from superior mesenteric artery)
• Body and tail: Branches of the splenic artery (dorsal pancreatic artery, great pancreatic artery - arteria pancreatica magna, caudal pancreatic arteries)

4. Microscopic Structure of the Pancreas

• Acini (acinar cells): Secretory units; pyramidal serous cells with basal rER and apical zymogen granules. Produce digestive enzymes (amylase, lipase, proteases as inactive zymogens).
• Duct system: Centroacinar cells lead to intercalated ducts → intralobular ducts → interlobular ducts → main pancreatic duct (of Wirsung) → minor duct (of Santorini).
• Secretion stimulated by CCK (acinar cells) and secretin (ductal cells produce bicarbonate-rich fluid).

• Scattered spherical clusters of cells (~1 million in total pancreas).
• Rich capillary network.
• Cell types:
  • Beta (β) cells (~70%): central location; produce insulin (hypoglycaemic)
  • Alpha (α) cells (~20%): peripheral; produce glucagon (hyperglycaemic)
  • Delta (δ) cells (~5-10%): produce somatostatin (inhibits both insulin and glucagon)
  • PP (F) cells (<5%): produce pancreatic polypeptide (inhibits exocrine secretion)
• Staining: Beta cells appear pale with Mallory stain (due to glycogen); distinguished by immunohistochemistry.

5. Embryological Basis of Annular Pancreas

• Dorsal bud: arises directly from the duodenum; forms the body, tail, and part of the head; its duct = accessory pancreatic duct (of Santorini).
• Ventral bud: arises from the hepatic diverticulum (common bile duct area); forms the uncinate process and part of the head; its duct = main pancreatic duct (of Wirsung).

• One part rotates normally (posteriorly)
• The other part rotates anteriorly around the duodenum
• The two parts fuse with the dorsal bud, creating a ring of pancreatic tissue encircling the 2nd part of the duodenum.
• This causes duodenal obstruction → neonatal vomiting, failure to thrive, bilious vomiting.
• In utero: prevents the fetus from swallowing amniotic fluid → polyhydramnios.
• Associated with Down syndrome and other congenital anomalies.
• Gray's Anatomy for Students, p. 397

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SPLEEN

1. Surfaces and Related Structures/Indentations

• Smooth, convex; lies against the diaphragm in the area of ribs IX-XI on the left.
• Related to the lower left thorax (ribs 9-11 and intercostal spaces).

• Gastric impression (anterior, large): related to the posterior surface of the stomach; has the notch on the superior border.
• Renal impression (posterior): related to the left kidney.
• Colic impression (inferior): related to the left colic flexure.
• Pancreatic impression: related to the tail of the pancreas at the hilum.
• Hilum: on the medial surface, where splenic vessels enter/exit and occasionally the tail of the pancreas reaches.

• Superior border: sharp, notched (characteristic palpable feature in splenomegaly)
• Inferior border: rounded
• Anterior end (superior pole)
• Posterior end (inferior pole)

2. Peritoneal Attachments of the Spleen

• Gastrosplenic ligament (gastrolienal): from the splenic hilum to the greater curvature of the stomach. Contains the short gastric arteries and left gastro-omental (gastroepiploic) vessels.
• Splenorenal ligament (lienorenal): from the hilum to the left kidney. Contains the splenic vessels and the tail of the pancreas.

• Phrenicosplenic ligament (phrenicolienal): from spleen to diaphragm (inconstant).
• Splenocolic ligament: from spleen to left colic flexure (inconstant).

3. Blood Supply of the Spleen

• Tortuous course along the superior border of the pancreas.
• Gives pancreatic branches (dorsal pancreatic, great pancreatic = arteria pancreatica magna, caudal pancreatic).
• Near the hilum, divides into 5-6 segmental arteries (splenic segments are avascular planes between them - used in partial splenectomy).
• Supplies the spleen and gives short gastric arteries and left gastroomental artery before the hilum.

• Runs posterior to the pancreas.
• Joined by the inferior mesenteric vein (usually).
• Unites with the superior mesenteric vein posterior to the neck of the pancreas to form the portal vein.

4. Surface Marking of the Spleen

• Lies in the left hypochondrium, against the diaphragm, in the region of ribs IX to XI posterolaterally.
• Its long axis follows the contour of rib X (10th rib).
• The posterior pole lies at the T10 vertebral level, medial to the angle of the 10th rib.
• Anterior pole extends to the midaxillary line.
• The superior pole is at the level of the superior pole of the left kidney (approximately T12).
• Rule of 1s: Measures approximately 1 inch thick, 3 inches wide, 5 inches long, weighs about 7 ounces (normal: 75-100 g, up to 150 g).
• The spleen is NOT normally palpable below the left costal margin. It must enlarge to at least twice its normal size before it becomes palpable.
• Gray's Anatomy for Students, p. 473

5. Histology of the Spleen

• Dense fibrous capsule with smooth muscle fibers.
• Trabeculae: carry trabecular arteries and veins.
• Reticular fibers (type III collagen) form the internal framework.

• Periarteriolar lymphoid sheath (PALS): surrounds central arteries; mainly T-lymphocytes (T-cell zone).
• Lymphoid follicles/Malpighian corpuscles: B-lymphocyte aggregates attached to PALS; may contain germinal centres after antigenic stimulation. Marginal zone surrounds follicles.

• Splenic sinusoids (venous sinuses): long, wide sinusoids lined by rod-shaped endothelial cells with elongated nuclei; have barrel-stave appearance on longitudinal section.
• Splenic cords (Billroth's cords): loose reticular tissue between sinusoids; contain macrophages, plasma cells, erythrocytes, granulocytes, platelets. Old/damaged RBCs are phagocytosed here.

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CLINICAL ANATOMY

1. Trauma to Left Hypochondrium/Lower Thorax → Massive Haemoperitoneum

• The spleen lies in the left hypochondrium against the diaphragm, related to ribs 9-11. It is a highly vascular organ with a very thin, fragile capsule that easily ruptures.
• The spleen is covered by visceral peritoneum and lies in the peritoneal cavity.
• Because the spleen has an exceptional blood supply (celiac trunk → splenic artery, ~200-300 mL/min), even a small tear causes rapid and copious bleeding directly into the free peritoneal cavity.
• Trauma to the left lower thorax (rib fractures at 9-11) transmits force directly to the underlying spleen.
• Delayed splenic rupture can occur if the capsule tamponades the initial bleed but then gives way days later.
• Blood accumulates rapidly in the dependent peritoneal recesses → massive haemoperitoneum.
• Gray's Anatomy for Students (Splenic rupture, p. 403): "Because the spleen has such an extremely thin capsule, it is susceptible to injury even when there is no damage to surrounding structures, and because the spleen is highly vascular, when ruptured, it bleeds profusely into the peritoneal cavity."

2. Pringle's Manoeuvre to Arrest Hepatic Bleeding

• All blood reaching the liver passes through the hepatoduodenal ligament - the free edge of the lesser omentum - before entering via the porta hepatis.
• The hepatoduodenal ligament contains: portal vein (posterior), hepatic artery proper (left), bile duct (right).
• The epiploic (omental) foramen lies posterior to the hepatoduodenal ligament, providing direct access to its posterior surface.
• Pringle's manoeuvre involves placing the index finger through the epiploic foramen and compressing the hepatoduodenal ligament between it and the thumb anteriorly.
• This compresses both the hepatic artery (arterial inflow) and the portal vein (portal inflow) simultaneously, reducing hepatic blood flow by ~75-80%, allowing the surgeon to control haemorrhage from hepatic lacerations.
• Safe ischaemia time: ~15-20 minutes (longer if intermittent).

3. Caput Medusae in Portal Hypertension

• When portal venous pressure rises (portal hypertension), blood seeks alternative routes back to the systemic circulation through porto-systemic anastomoses.
• The para-umbilical veins travel in the round ligament of the liver (ligamentum teres), connecting the left branch of the portal vein to the periumbilical region of the anterior abdominal wall.
• From the umbilicus, these dilated veins radiate outward and connect with:
  • Superior epigastric veins → internal thoracic → SVC (superior direction)
  • Inferior epigastric veins → external iliac → femoral → IVC (inferior direction)
  • Lateral thoracic/thoracoepigastric veins → axillary → subclavian → SVC
• The result is a radiating pattern of dilated superficial veins around the umbilicus - resembling the snakes on Medusa's head ("caput medusae").
• Blood flow direction: away from the umbilicus in all directions (distinguishes it from inferior vena cava obstruction where flow is upward).

4. Tumour in Head of Pancreas → Jaundice, Dark Urine, Pale Stools (Courvoisier's sign)

• The common bile duct in its infrapancreatic/pancreatic part runs in a groove or tunnel through the posterior surface of the head of the pancreas before entering the 2nd part of the duodenum.
• A tumour in the head of the pancreas compresses or directly invades this segment of the bile duct → obstructive (posthepatic) jaundice.
• Consequences of biliary obstruction:
  • Bile (conjugated bilirubin) cannot enter the intestine → accumulates in blood → jaundice (yellow sclera/skin).
  • Conjugated bilirubin is water-soluble → excreted by kidneys → dark (tea-coloured) urine (bilirubinuria).
  • Absent bile in intestine → no stercobilinogen produced → pale/clay-coloured stools (acholia).
  • Also: steatorrhoea (absent bile salts for fat digestion), malabsorption.
• Courvoisier's Law: In painless obstructive jaundice with a palpably enlarged, non-tender gallbladder, the cause is most likely malignancy (e.g., head of pancreas carcinoma) rather than gallstones. Because gallstone obstruction is usually preceded by chronic cholecystitis, the gallbladder wall is fibrotic and cannot distend.
• Gray's Anatomy for Students, p. 474

5. Murphy's Sign - Anatomical Basis

• The gallbladder normally lies on the visceral surface of the right lobe of the liver, in its fossa between the right and quadrate lobes.
• Its fundus projects at the junction of the right lateral border of the rectus abdominis and the right costal margin (9th costal cartilage) - the McBurney-gallbladder point.
• In acute cholecystitis, the gallbladder becomes inflamed and tender (visceral peritoneum becomes involved).
• On deep inspiration, the diaphragm descends, pushing the liver (and inflamed gallbladder) downward toward the examiner's fingers.
• Contact between the inflamed gallbladder and the examining fingers causes sudden sharp pain, causing the patient to involuntarily stop (catch) their breath (inspiratory arrest) - a positive Murphy's sign.
• It is positive in acute cholecystitis, negative in chronic cholecystitis and in conditions that mimic it.

6. Gallstone Ileus - Anatomical Basis

1. A large gallstone (usually >2.5 cm) causes repeated episodes of cholecystitis, leading to adhesions between the inflamed gallbladder and adjacent bowel (usually 1st/2nd part of duodenum or, less commonly, hepatic flexure of colon).
2. Pressure necrosis from the gallstone erodes through the gallbladder wall and into the adherent bowel wall, creating a cholecystoduodenal fistula (most common), cholecystocolic, or other bilioenteric fistula.
3. The gallstone passes into the duodenum and enters the small intestine.
4. It passes freely through the jejunum and most of the ileum (bowel lumen widens proximally).
5. It impacts at the terminal ileum (narrowest point, ~2.5 cm diameter, and the ileocaecal valve further restricts passage) → obstruction.
6. The Rigler triad on plain X-ray: small bowel obstruction + pneumobilia (air in biliary tree) + ectopic gallstone.

7. Preservation of Tail of Pancreas During Pancreatectomy

• The tail of the pancreas is the only part that is intraperitoneal (within the splenorenal ligament).
• All other parts of the pancreas are secondarily retroperitoneal - they have lost their mesentery and are adherent to the posterior abdominal wall, making them technically difficult to mobilize without damaging adjacent structures (IVC, aorta, portal vein, superior mesenteric vessels, etc.).
• The tail, being mobile within the splenorenal ligament, can be mobilized and preserved more easily during surgery.
• Preserving the tail also preserves the islets of Langerhans in that region, reducing the risk of post-operative diabetes mellitus.
• The tail is also tightly associated with the splenic hilum; preservation requires careful dissection to avoid injury to the splenic vessels. If the spleen is being preserved, the tail must be handled carefully.

8. Pseudocyst of Pancreas Develops Within the Lesser Sac

• The pancreas lies against the posterior wall of the lesser sac (omental bursa). The anterior surface of the pancreatic body is covered by peritoneum that forms the posterior wall of the lesser sac.
• In acute pancreatitis, inflammatory enzymes (particularly trypsin) autodigest the pancreatic parenchyma and surrounding tissue, causing leakage of pancreatic juice and blood.
• This fluid is released directly into the lesser sac, which is a potential space between the stomach/lesser omentum anteriorly and the posterior peritoneum/pancreas posteriorly.
• The lesser sac has limited communications (only through the epiploic foramen) → fluid becomes walled off by surrounding peritoneal inflammation and fibrous tissue.
• The collection has no epithelial lining (hence "pseudo"cyst - a true cyst would have an epithelial lining).
• The pseudocyst can expand into the greater sac through the epiploic foramen, or remain confined.
• Large pseudocysts may displace the stomach anteriorly or compress adjacent structures (bile duct, duodenum, vessels).

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