Hepatic functional anatomy

Liver tissue

The histological unit of the liver is the lobule (a central vein, surrounded by a hexagon of tissue).

The functional unit it the acinus, a rhombus formed by two portal triads (arteriole, portal venule, bile duct) and two central veins.

There are three zones formed by falling tissue oxygen tension

1. Highest PO2. High metabolic rate. Synthesizes proteins, secretes glucose.
2. Intermediate PO2 and function.
3. Low PO2. Injured first in shock. \(\uparrow\)[CYP450], site of drug metabolism. Absorbs and utilizes glucose.

The hepatic sinusoid

Origin: union of portal venule and hepatic arteriole

Termination: joins central vein

Fenestrated epithelium with absent basement membrane.

Kuffner cells (resident macrophages) and Pitt cells (resident NK cells) sit on the endothelium, in the vessel. Kuffner cells phagocytose anything opsinized (yummy yummy).

Beneath the endothelium is the thin space of Disse, which contains Ito cells (contractile cells that modulate sinusodal capacitance and store fat-soluable vitamins).

Beneath that is hepatocytes.