Terminal hepatic venule

Classically the liver has been divided into hexagonal lobules centred around the terminal hepatic venules. Blood enters the liver through the portal tracts that are situated at the corners of the hexagon. The portal tracts are triads of a portal vein, an hepatic artery, and a common hepatic bile duct. The vast expanse of hepatic tissue, mostly consisting of parenchymal cells (PC) or hepatocytes, is serviced via terminal branches of the portal vein and hepatic artery, which enters the tissue at intervals. The hepatocytes are organized into cords of cells radially disposed about the central hepatic venule. Between these cords are vascular sinusoids that transport the blood to the central hepatic venules. The blood is collected through the hepatic venules into the hepatic vein which exits the liver into the inferior vena cava (Figure 4.1). 

Figure 28.1. Comparison of structural liver lobule with functional acinar regions. The liver lobule is centered on the terminal hepatic venule (THV), also called the central vein, and assumes a roughly hexagonal shape with its vertices at the portal triads, which contain the portal vein (PV), hepatic artery (HA), and bile duct (BD). The liver acinus is centered upon the tract of blood vessels that branch from the hepatic artery and portal vein of the portal triads. Hepatocytes within the acinus are grouped within functional zones 1,2, and 3 located at increasing distances from the vascular tracts that interconnect adjacent portal triads.

Fibrosis As a consequence of the necroinflammatory process, fibrogenesis is activated (s. p. 403) it begins in the portal fields and leads to their fibrotic dilation. Fibrosis extends to the periportal zones and can ultimately link portal tracts to other portal tracts and to terminal hepatic venules. Reliable staging requires con-... 

Figure 3 Schematic representation of a simple hepatic acinus. PS is the portal space, consisting of a branch of the portal vein, a hepatic arteriole, and a bile duct THV is the terminal hepatic venule (central vein) 1, 2, and 3 represent the various zones surrounding the terminal afferent vessel. (Reproduced with permission from Klassen CD, Amdur MO, and Doull J (eds.) (1986) Casarett and Doull s Toxicology The Basic Science of Poisons, 3rd edn. New York McGraw-Hill The McGraw-Hill Companies, Inc.)...

Unlike mammals, fish do not appear to exhibit a defined relationship between portal spaces and terminal hepatic venules. This apparent lack of organization also has been reported on the biochemical level. Enzymatically, heterogenous zones of hepatocytes as found in mammals are not evident in fish (35,36). In addition hepatic perfusion is poor in fish with rates 1/2 to 1/4 of those found in mammals. These features may be important in regards to metabolism and toxicity of xenobiotics. 

The bile canaliculi form a network, which feed into ductules, which become bile ducts (Fig. 6.3). The structural and functional unit of the liver is the lobule, which is usually described in terms of the hepatic acinus (Fig. 6.5), based on the microcirculation in the lobule. When the lobule is considered in structural terms, it may be described as either a classical or a portal lobule (see "Glossary"). The acinus comprises a unit bounded by two portal tracts and terminal hepatic or central venules, where a portal tract is composed of a portal venule, bile ductile, and hepatic arteriole (Fig. 6.5). Blood flows from the portal tract toward the central... 

Lobular inflammation Whereas lobular, diffusely distributed inflammation is more evident, in acute hepatitis portal and periportal inflammation predominates in chronic hepatitis and lobular hepatitis is less pronounced. Generally, it consists of separate small clusters of mononuclear cells. Scattered necrotic hepatocytes (= acidophilic / Councilman bodies) are found the hepatocellular nuclei are in disarray (= anisonucleosis) there is swelling of the hepatocytes, and mitoses are present. Marked lobular hepatitis in conjunction with considerable portal and periportal inflammation is typical of flares of chronic viral hepatitis or autoimmune hepatitis. In addition to single-cell necroses, there are confluent necroses, which affect entire lobules. Bridging necroses link portal tracts with other portal tracts or with terminal venules, (l)... 

A 28-year-old man presented with jaundice after taking six tablets of skullcap (together with zinc and pau d arco) daily for the previous 6 months to help his multiple sclerosis. His liver enzjmes were raised and hepatitis A, B, and C serologies were negative. He developed progressive liver failure and received a transplant but died shortly after. His explanted hver showed fibrous stenosis and obliteration of most of the terminal venules with extensive perivenular fibrosis, indicative of veno-occlusive disease. 

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