Terminal hepatic vein

Fig. 2.14 Diagram of the functional (microcirculatory) liver unit ( simple acinus ) (A.M. Rappaport, 1960, 1963) terminal hepatic vein (thV), periportal field (P), zones of different blood supply A, B, C and 1, 2, 3. Zone 1 (afferent zone) zone richest in O2, nutrients and hormones. Zone 3 (efferent zone) zone poorest in O2, nutrients and hormones, but enriched with CO2 and metabolites from zones 1 and 2. (Direction of blood flow is from 1 to 3 and from A to C)...

Fig. 2.15 Diagram of the liver lobule and the acinus arranged like a clover leaf around the portal field according to the acinar structure (modified from D. Sasse, t986) central hepatic vein (CV) or terminal hepatic vein, periportal field (P). Circulatory and meta-bolically different zones zone t (periportal), zone 2 (intermediate), zone 3 (perivenous)...

A 23-year-old man with acute lymphocytic leukemia took tioguanine for 10 months and developed intense sinusoidal engorgement which resolved on withdrawal with some residual subintimal fibrosis around the terminal hepatic veins (12). 

The functional anatomical unit of the hver is the acinus, adjacent to the portal triad, which consists of a branch of the portal vein, hepatic artery, and bile duct. Each acinus is a diamond-shaped mass of liver parenchyma that is supplied by a terminal branch of the portal vein and of the hepatic artery and drained by a terminal branch of the bile duct. The blood vessels radiate toward the periphery, forming sinusoids, which perfuse the liver and ultimately drain into the central (terminal) hepatic vein (Figure 47-2). The sinusoids... 

Microscopically, EHE is a solid tumor composed of epithelioid-appearing endothelial cells. There are dendritic spindle cells and epithelioid round cells within an abundant matrix of myxoid and fibrous stroma. Neoplastic cells invade and eventually obliterate the sinusoids, terminal hepatic veins, and portal veins. Approximately 30% of patients may demonstrate progressive sclerosis and eventual classification (Kelleher et al. 1989). The demonstration of cells containing factor Vlll-related antigen confirms the endothelial origin of the tumor. 

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.

In the porta hepatis, the proper hepatic artery divides into the right branch (from which the cystic artery emerges) and the left branch (from which a middle hepatic artery occasionally emerges). The branches of the hepatic artery run close to the portal veins and may even (rarely) coil round them in places. An arterial sphincter is located prior to the further division of the hepatic artery into smaller branches. There are anastomoses between the arterial branches and the hepatic vein. By way of an arteriolar sphincter (46), the interlobular arteries branch into intralobular arterioles, supplying the lobules of the liver with arterial blood. The arterial blood enters the sinusoids either through terminal branches or through arterioportal anastomoses and mixes with the portal blood. The pressure in the hepatic arterioles is 30-40 mm Hg. (36, 46, 61)... 

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.)...

Menaquinones are absorbed mainly from the terminal ileum, where bile salts are present, into the hepatic portal vein. Litde of the menaquinones formed by colonic bacteria can be absorbed, because they remain tightly bound to bacterial cell membranes in the absence of bile salts. About 90% of the total liver content of vitamin K is menaquinones 7 to 13, and the hepatic pool of phylloquinone turns over considerably faster than that of menaquinones. Sixty percent to 70% of the daily intake of phylloquinone is excreted, mainly as conjugates in the bile, and the half-life of a tracer dose of phylloquinone is only about 17 hours. 

In the portal tract (= Glisson s triangle, portal field) (E Glisson, 1659), the perivascular connective tissue with its enclosed (and protected) radicles of the portal veins, the hepatic arterioles, bile ducts, lymph vessels and nerve fibres terminates in the connective tissue covering of the... 

The functional and microcirculatory hepatic unit forms the basis for assessing the hepatic acinus (A. M. Rappaport, 1954). (41-43) The portal vascular bundle, with the terminal branches of the hepatic artery and portal vein diverging fan-shaped after penetrating the lobules, is at the centre of the acinar structure. These vessels represent the central axis for the circular blood supply of the related liver parenchyma. This area is roughly the shape of a rhombus, the outer angles of which are formed by the two central veins of the adjacent lobules while the diagonal... 

Fig. 2.13 Diagram of the classic hepatic lobule (I), the portal vein lobule (II) and the hepatic acinus (III) CV = central vein ( ), P = portal tract ( ). Flow direction venous blood (= blue arrow), arterial blood (= red arrow) and bile (= green arrow), with the microcirculatory acinus zones 1, 2, 3. (cf. W Ekataksin et af, 1992 the microvascular unit is regarded as an area in which all hver cells receive blood from a common terminal vessel)...

Figure 2 Diagram illustrating the basic functional unit of the liver, the acinus, consisting of the tissue centered around the terminal branches of the hepatic artery and portal vein. The cells in zone 1 nearest these vessels receive the highest concentrations of oxygen and nutrients, while those in zones 2 and 3 are exposed to progressively depleted blood. (Reproduced from Bloom W and Fawcett DW (eds.) (1968) A Textbook of Histology, 9th edn. Philadelphia Saunders, with permission redrawn from Rappaport A et al. (1954) The Anatomical Record 11.)...

The lobes of the liver are divided into smaller lobules with a roughly hexagonal arrangement of hepatocytes around a central vein. At the vertices of the lobules are bile ducts, terminal branches of the hepatic artery, and portal veins—termed the portal triad. Connective stromal tissues extend throughout the liver, providing support for cells and routes for blood vessels, lymphatic vessels, and bile ducts. The hepatocytes form groups of cells around small branches of the portal vein, hepatic arteriole, bile duct, lymph vessel, and nerves this functional unit is called an acinus (plural acini). The acini form part of a larger structure, which can be divided into three zones ... 

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