Fenestrated endothelium, Kupffer cells and stellate cells
Expansion
The sinusoid is a discontinuous, fenestrated capillary with no basement membrane, which allows plasma free access to the hepatocyte surface.
The space of Disse lies between the sinusoidal endothelium and the hepatocytes. It contains:
- Hepatic stellate (Ito) cells - store vitamin A in health
- Microvilli of the hepatocyte surface
- The origin of hepatic lymph, which is why the liver produces a large proportion of thoracic duct lymph, and why ascites forms readily in cirrhosis
Kupffer cells are the resident macrophages, lying within the sinusoidal lumen, clearing bacteria and aged red cells from portal blood.
“Stellate cells are the origin of cirrhosis.” In chronic injury they lose their vitamin A, transform into myofibroblasts, and deposit collagen in the space of Disse. This capillarises the sinusoid, losing its fenestrations and gaining a basement membrane, which both impairs exchange and raises resistance, producing portal hypertension.
Blood flows from the portal triad to the central vein, so oxygen falls across the acinus: zone 1 (periportal) is best oxygenated and first affected by ingested toxins and viral hepatitis; zone 3 (centrilobular) is least oxygenated and most vulnerable to ischaemia and paracetamol, which is why both produce centrilobular necrosis.