Normal Liver Anatomy and Physiology

Comprehensive vocabulary flashcards covering normal liver anatomy, peritoneal coverings, lobar and segmental divisions, vascular supply, microarchitecture, metabolic and detoxification functions, clinical liver function tests, and anatomical variants.

Glisson Capsule

A thin fibrous casing deep to the peritoneal membrane that is thickest around the inferior vena cava (IVC) and porta hepatis, serving as a pathway for blood vessels, nerves, and lymphatics.

Bare Area of the Liver

The posterosuperior surface of the liver that lacks a peritoneal covering, situated directly against the diaphragm and bordered by the coronary ligaments.

Main Lobar Fissure

The anatomic dividing landmark separating the true right and left lobes of the liver, housing the middle hepatic vein (MHV) and gallbladder fossa.

Right Intersegmental Fissure

The fissure that divides the right liver lobe into anterior and posterior segments; the right hepatic vein (RHV) courses through it.

Left Intersegmental Fissure

The fissure that divides the left liver lobe into medial and lateral segments; it contains the left hepatic vein (LHV) and the ascending portion of the left portal vein (LPV).

Caudate Lobe

The lobe situated on the posterior aspect of the liver, bordered anteriorly by the ligamentum venosum and posteriorly by the inferior vena cava (IVC), possessing autonomous vascular inflow and venous drainage directly into the IVC.

Falciform Ligament

A peritoneal fold extending from anterior to posterior through the liver that anchors it to the anterior abdominal wall and divides the right and left subphrenic spaces.

Ligamentum Teres (Round Ligament)

The fibrous cord formed by the atrophy of the fetal umbilical vein after birth; it lies within the free inferior margin of the falciform ligament.

Ligamentum Venosum

The fibrous remnant of the fetal ductus venosus (which shunts blood from the umbilical vein to the IVC); it runs posterior to the portal bifurcation and marks the anterior boundary of the caudate lobe.

Coronary Ligaments

Peritoneal reflections consisting of anterior and posterior leaves that attach the posterior right liver to the diaphragm and surround the bare area.

Hepatoduodenal Ligament

The thick portion of the lesser omentum connecting the liver to the duodenum that encloses the portal triad and forms the anterior boundary of the epiploic foramen.

Gastrohepatic Ligament

The portion of the lesser omentum extending between the posterior superior liver and the lesser curvature of the stomach.

Dual Blood Supply of the Liver

The vascular system whereby the liver receives $20\text{--}30\%$ of its oxygenated blood via the hepatic artery and $70\text{--}80\%$ of its partially oxygenated, nutrient-rich blood via the main portal vein.

Main Portal Vein (MPV)

The vessel formed by the confluence of the superior mesenteric vein and the splenic vein that brings nutrient-rich, deoxygenated blood to the liver for filtering.

Hepatic Veins

Three large intersegmental veins (right, middle, and left) that drain deoxygenated, filtered hepatic blood directly into the inferior vena cava and right atrium.

Bunny Sign

The ultrasound appearance in a transverse plane showing the right, middle, and left hepatic veins converging into the inferior vena cava, resembling rabbit ears.

Intrasegmental Vessels

Vessels that course directly through the center of hepatic segments, represented by the portal triad branches (portal vein, hepatic artery, and bile duct).

Intersegmental Vessels

Vessels that travel between liver lobes and segments, represented anatomically by the hepatic veins.

Couinaud Classification System

A functional anatomical system dividing the liver into 8 independent segments, each possessing its own independent dual vascular inflow, biliary drainage, and lymphatic drainage.

Segment I (Couinaud)

The caudate lobe, which possesses unique autonomous portal and arterial branches and drains directly into the inferior vena cava rather than through the major hepatic veins.

Segment IV (Couinaud)

The medial segment of the left hepatic lobe located between the left and middle hepatic veins, divided into superior (IVa) and inferior (IVb) subsegments.

Classical Hepatic Lobule

The microscopic, hexagon-shaped functional unit of the liver organized around a central vein with radiating plates of hepatocytes and peripheral portal triads.

Hepatic Sinusoids

Specialized, wide-diameter fenestrated capillaries located between cords of hepatocytes that permit the rapid exchange of nutrients, waste, and oxygenated blood.

Kupffer Cells

Resident liver macrophages situated within sinusoidal linings that phagocytize bacteria, damaged red blood cells, and foreign debris as part of the immune defense.

Space of Disse

The perisinusoidal space between hepatocytes and sinusoidal endothelial cells containing extracellular fluid and microvilli; it serves as the primary production site of hepatic lymph.

Stellate Cells (Ito Cells)

Fat-storing cells located in the space of Disse that store vitamin A and undergo myofibroblastic activation to secrete collagen and produce fibrosis in response to liver injury.

Portal Triad

A peripheral structural triad present at the corners of hepatic lobules consisting of an interlobular bile duct, a branch of the hepatic portal vein, and a branch of the hepatic artery.

Unconjugated Bilirubin (Indirect Bilirubin)

A lipid-soluble, non-water-soluble pigment derived from hemoglobin breakdown that must circulate bound to albumin before hepatic uptake.

Conjugated Bilirubin (Direct Bilirubin)

Water-soluble bilirubin glucuronide formed in hepatocytes by attaching glucuronic acid via the enzyme UDPGT, which is subsequently secreted into bile canaliculi.

Enterohepatic Circulation

The recycling process in which up to $95\%$ of cholesterol-based bile salts secreted into the duodenum are reabsorbed in the ileum and returned to the liver via the portal vein.

Glycogenesis

The insulin-stimulated metabolic conversion of excess blood glucose into glycogen stored within hepatocytes.

Glycogenolysis

The enzymatic breakdown of stored hepatic glycogen into glucose, stimulated by glucagon and epinephrine during fasting or exercise to maintain blood sugar.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate precursors such as amino acids (e.g., alanine), glycerol, and lactate during periods of starvation or fasting.

Urea Cycle

The enzymatic pathway occurring in the mitochondria and cytoplasm of liver cells that converts toxic ammonia from amino acid deamination into less toxic urea for excretion by the kidneys.

Alanine Aminotransferase (ALT)

An intracellular liver enzyme formerly called SGPT; it is a highly specific laboratory indicator of hepatocellular damage and necrosis.

Aspartate Aminotransferase (AST)

An intracellular enzyme formerly called SGOT found in liver, cardiac, and skeletal muscle tissue; elevated serum levels indicate acute tissue or cellular injury.

Alkaline Phosphatase (ALP)

An enzyme present in bile ductular epithelial cells, bone, kidneys, and the placenta; marked elevation in serum is characteristic of biliary tract obstruction.

Gamma-Glutamyl Transferase (GGT)

A microsomal enzyme located in the liver, pancreas, and kidneys that serves as the most sensitive indicator for alcohol damage to the liver.

Prothrombin Time (PT)

A laboratory measurement of blood coagulation time reflecting the hepatic synthesis of vitamin K-dependent clotting factors; increased PT indicates liver synthesis dysfunction.

Albumin

The primary plasma protein synthesized by the liver, essential for maintaining intravascular colloid osmotic pressure; reduced levels allow fluid leakage into the peritoneal cavity causing ascites.

Alpha-Fetoprotein (AFP)

An oncofetal protein synthesized by rapidly dividing embryonic hepatocytes; in adults, markedly elevated levels serve as a tumor marker for hepatocellular carcinoma and testicular or ovarian cancers.

Carcinoembryonic Antigen (CEA)

A glycoprotein normally produced in fetal gastrointestinal tissue; reappearance in adult serum serves as a non-specific tumor marker for gastrointestinal and metastatic liver malignancies.

Riedel's Lobe

A normal anatomical variant characterized by a tongue-like or finger-like inferior projection of the anterior margin of the right liver lobe extending past the lower pole of the right kidney, occurring more commonly in women.

Beaver Tail Liver

An anatomical variant where an elongated left lobe extends laterally into the left upper quadrant to contact or wrap around the spleen; also referred to as a sliver of liver.

Situs Inversus Totalis

A congenital condition marked by a complete mirror-image transposition of all thoracic and abdominal viscera, causing the liver to be located in the left upper quadrant (LUQ).