Page 411 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat

Gastrointestinal ` gastrointestinal—anatomy Gastrointestinal ` gastrointestinal—anatomy seCtion iii 367

Liver tissue The functional unit of the liver is made up of Zone I—periportal zone:
architecture hexagonally arranged lobules surrounding the ƒ Affected 1st by viral hepatitis
central vein with portal triads on the edges ƒ Best oxygenated, most resistant to circulatory
A
(consisting of a portal vein, hepatic artery, bile compromise
ducts, as well as lymphatics) A . ƒ Ingested toxins (eg, cocaine)
Apical surface of hepatocytes faces bile Zone II—intermediate zone:
canaliculi. Basolateral surface faces sinusoids. ƒ Yellow fever
Kupffer cells (specialized macrophages) located Zone III—pericentral vein (centrilobular) zone:
in sinusoids (black arrows in B ; yellow arrows ƒ Affected 1st by ischemia (least oxygenated)
show hepatic venule) clear bacteria and ƒ High concentration of cytochrome P-450
B damaged or senescent RBCs. ƒ Most sensitive to metabolic toxins (eg,
Hepatic stellate (Ito) cells in space of Disse ethanol, CCl , halothane, rifampin,
4
store vitamin A (when quiescent) and produce acetaminophen)
extracellular matrix (when activated). ƒ Site of alcoholic hepatitis
Responsible for hepatic fibrosis.

Blood flow Bile flow

Sinusoids Hepatic vein
Hepatic
vein Endothelial
cells

Stellate cell
Zone 3
Zone 2
Space of Disse
Zone 1

Zone 1
Kup er cell
Zone 2
Zone 3

Branch of
hepatic artery
Branch of
portal vein
Bile ductule
Portal triad

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