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Liver notes: Zones and Lobes


LOBULES
centered around portal triad: hep artery, portal vein, bile duct
portal vein and hepatic artery both drain into sinusoid
sinusoid has gaps between ECs, bigger than the fenestrations of the glomerulus
RBC's and immune cells can leak through these gaps
sinusoid drains into central vein-->hepatic vein-->IVC-->right heart
if right heart fails-->congestive hepatomegaly, nutmeg liver

ZONES
1-3 as it leaves the hepatic arteries (in triad) and drains toward the hepatic veins
cells are specialized in each zone

ZONE I: PERIPORTAL
most O2 because closes to hepatic arteries
most susceptible to toxic injury
hepatocytes specialized for oxidative liver fx: gluconeogenesis, β-oxidation of fas and chol syn
hemosiderin deposits here in hemochromatosis

ZONE II: TRANSITION ZONE
necrosis in yellow fever (flavivirus, single strand +RNA)

ZONE III: CENTRILOBULAR
least 02, closest to central veins
detoxifying zone: most cyp450 activity
where fatty change happens??
most sensitive to hypoxic and ischemic injury
fx: glycolysis, lipogenesis and cytochrome P-450-based drug detoxification
highest concentration of CYP2E1-->most sensitive to NAPQI production in acetaminophen toxicity
this is the area most impacted in R heart failure

LOBES OF THE LIVER
caudate lobe, quadrate lobe, left lobe, and right lobe
left and right are anterior
gall bladder is up against right lobe?
plane from gallbladder fossa to IVC separates true right and left lobes?
falciform ligament divides left from right?
caudate and quadrate are posterior
back of liver is visceral surface
caudate is above quadrate with transverse fissure aka porta hepatis between them
from behind lobes divided by ligamentum venosum and ligamentum teres
saggital fossa contains IVC, separates caudate and quadrate from right lobe

METABOLIC PERSPECTIVE
functional unit is the hepatic acinus
each acinus is centered on the line connecting two portal triads
extends outwards to the two adjacent central veins

Where there is love of medicine, there is love of humankind.
-- Hippocrates

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