CorpusHuman Anatomy

Liver Lobule

Classic hexagonal lobule, portal triads, sinusoids and acinar zones

A classic hepatic lobule: a hexagonal prism about 1–2 mm across, centred on a central vein, with portal triads at its corners. Each triad holds a portal venule, a hepatic arteriole and a bile ductule. Plates of hepatocytes radiate from the centre, with sinusoids between them. Mixed portal-venous and arterial blood (animated dots) flows inward along the sinusoids to the central vein. Bile (green dashes) is secreted into canaliculi between the hepatocytes and flows outward, the opposite way, to the bile ductules of the triads. Kupffer cells (green) sit in the sinusoids.

The shaded triangle shows the acinar zones of Rappaport. Zone 1 (periportal) receives the most oxygen and nutrients. Zone 3 (centrilobular) receives the least oxygen and has the most cytochrome P450, which is why ischaemia, paracetamol toxicity and venous congestion hit it first. The right panel magnifies one sinusoid. It shows the fenestrated endothelium without a basement membrane, the space of Disse with hepatocyte microvilli and a vitamin-A-storing stellate (Ito) cell, a Kupffer cell in the lumen, and a bile canaliculus sealed by tight junctions between two hepatocytes.

Step-by-step

  1. The classic lobule

    A hexagonal unit about 1–2 mm across, with a central vein at its centre and portal triads at its corners. The human liver contains roughly 50,000–100,000 lobules.

  2. Portal triad

    Each corner carries a portal venule (about 75% of inflow, nutrient-rich), a hepatic arteriole (about 25%, oxygen-rich) and a bile ductule, with lymphatics and nerves.

  3. Hepatocyte plates and sinusoids

    Plates of hepatocytes, one to two cells thick, radiate from the central vein. Blood from both inflow vessels mixes in the sinusoids between the plates.

  4. Blood flows inward

    Sinusoidal blood flows centripetally from the triads to the central vein, then to the hepatic veins and the IVC, exchanging with every hepatocyte on the way.

  5. Bile flows outward

    Hepatocytes secrete bile into canaliculi, channels between adjacent cells sealed by tight junctions. Bile flows centrifugally, opposite to the blood, to the bile ductules in the triads.

  6. The sinusoid wall

    Fenestrated endothelium with no basement membrane lets plasma into the space of Disse, where hepatocyte microvilli absorb and secrete. Stellate (Ito) cells there store vitamin A and drive fibrosis when activated.

  7. Kupffer cells

    Resident macrophages in the sinusoid lumen. They filter bacteria and endotoxin from portal blood and remove aged red cells.

  8. Acinar zones

    Zone 1 (periportal) is oxygen-rich. Zone 3 (centrilobular) is hypoxic and rich in CYP450, so it is the first to necrose in shock, paracetamol overdose and congestion.

Labelled parts