Liver lobules

I. M. Anundi, F. C. Kauffman, M. El-Mouelhi, R. G. Thurman, Hydrolysis of Organic Sulfates in Peripheral and Pericentral Regions of the Liver Lobule Studies with 4-Meth-ylumbelliferyl Sulfate in the Perfused Rat Liver , Mol. Pharmacol. 1986, 29, 599 - 605. 

Studies in mice have shown that selective covalent binding of VDC occurs in the proximal tubules, the liver lobules, and the mucosa of the upper respiratory tract and corresponds to sites of potential toxicity. Additional events such as depletion of glutathione appear to be necessary for VDC-induced cell death to occur. 

Which of the following are true Compared with zone 1, zone 3 of the liver lobule has... 

Centrilobular The region of the liver lobule surrounding the central vein. 

Belinsky SA, Matsumura T, Kauffman FC, et al. 1984. Rates of allyl alcohol metabolism in periportal and pericentral regions of the liver lobule. Mol Pharmacol 25 158-164. 

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.

Figure 1.4 The classic liver lobule (Dr Desley Neil, Department of Cellulor Pathology, University Hospital Birmingham NHS Foundation Trust).

Figure 2.3. Blood circulation and tissue perfusion in the liver, a Schematic of the blood circulation. Portal vein and liver artery branch out in a parallel fashion. From the terminal branches, the blood enters the tissue and is then eollected into the tributaries of the liver vein, b The liver tissue has a honeyeomb stmcture each hexagon is a liver lobule. The liver artery and portal vein branches are located at the comers in the middle of the lobule, we find the central vein which merges with others to form the liver vein, c Higher power view, showing the sponge-like stmcture of the liver tissue. The blood gains intimate contact with virtually every liver cell - diffusional barriers are absent, and distances extremely short.

S.Th. Sommering defined the total mass of the liver lobule as acinus on the grounds that it was composed solely of vessels (cf M. MALPiom, 1666). 

Description of the hexagonal architecture of the liver lobule and of the anastomoses of the fine bile capillaries by F. Kiernan. (s. fig. 1.18)... 

Fig. 1.18 Illustration of liver lobules and vessels by F. KmRNAN, 1833 (a, b interlobular veins, c intralobular vein plexus, d intralobular branch of the central hepatic vein) (13)...

J. Henle describes the bile canaliculi in the liver lobules as simple, unwalled intracellular spaces. 

The term parenchyma referring to the liver tissue was coined by Erasistratos. The liver lobules were first described in the pig in 1664 by XX Wepfer (using microscopic techniques) while the lobular structure was confirmed by M. Malpighi in 1666. The term acinus was coined by S.Th. Sommering in 1796. However, it was F. Kiernan (1833) who first gave a classic definition of the lobule in pig liver ( hepatic lobule ). Today, such anatomical clarity can only be found in the livers of the camel, polar bear and seal. (s. fig. 1.18)... 

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)...

The morphological unit is the liver lobule. With regard to the histological evaluation of a liver biopsy specimen, the use of this lobular structure is imperative to pathologist and clinician alike. 

The urea cycle, also called ornithine cycle, was first described by H.A. Krebs and K. Henseleit in 1932. (quot. 51) The principle of ammonia detoxification in the urea cycle is based on the conversion of ammonium and bicarbonate in the mitochondria under ATP consumption into carbamoyl phosphate (by means of carbamoyl phosphate synthetase). It enters the urea cycle, which is localized mainly - yet with a low affinity for ammonium - in the periportal zone of the liver lobule. In the urea cycle alone, about two thirds of the amino nitrogen of ammonia are irretrievably lost to the organism (= definitive ammonia detoxification), (s. fig. 3.12)... 

There is no y-GT activity in muscle, bone and erythrocytes. Despite high y-GT activity in kidneys, nephropathies do not result in y-GT elevations. During pregnancy, y-GT activity is normal or the serum values may show a declining tendency from the second trimester onwards. In the liver, y-GT is found in the membranes of hepatocytes and bile duct epithelia. The periphery of the liver lobule has the highest y-GT activity. Gamma-GT passes from the liver into the bile and is then excreted partly by the kidneys in the urine, (s. tabs. 5.4, 5.5)... 

Among the experimentally tested transplantation sites are the spleen, kidneys, lungs, pancreas, peritoneum, greater omentum and fatty tissue. Up to now, the spleen has proved to be the most suitable. The transplantation of foetal liver cells into the spleen may even culminate in a liver lobule-like formation with bile ducts and veins — however, the functional results have (so far) been no better than with normal hepatocytes. 

Granulomas are generally distributed focally throughout the liver, mostly within the liver lobules and less frequently in the portal fields. As a rule, the normal lobular architecture is not affected. Granulomas located on the surface can be visualized laparoscopically as small, greyish-white foci, which can be conveniently collected by forceps biopsy for histological examination. 

LC These liver-specific antibodies (LCl and LC2) react with a soluble cytosolic antigen in the liver cells (W. Storch, 1975, 1979). This was confirmed by E. Martini et al. in 1982. They are frequently associated with anti-LKM 1 antibodies (60-70%). The hepatocytes around the central vein of the liver lobule are left out of the otherwise homogeneous cytoplasmatic fluorescence. LC 1 antibodies are not present in chronic viral hepatitis C, and thus they are important in differentiating between (LCl-positive) AIH and (LCl-negative) chronic HCV infection. LCl is primarily found in young patients presenting with AIH type 2. Only rarely are LC2 antibodies found in AIH they react with periportal liver cells. (35, 45)... 

The histological criteria of chronic hepatitis are (1.) liver cell damage, (2.) inflammatory infiltration, and (S.) fibrosis formation. These chronic inflammatory reactions affect firstly the portal field, then the periportal region (i.e. zone 1) and finally the liver lobule. Such reactions constitute a dynamic process, whereby the intensity of the above-mentioned criteria as well as their topographical distribution pattern in the portal, periportal and azinar area vary considerably. (14, 16)... 

Figure 1 Diagram illustrating the basic anatomical unit of the liver, the liver lobule, showing (1) the radial disposition of the liver cell plates and sinusoids around the central vein, (2) the centripetal flow of blood from branches of fhe hepafic artery and portal vein, and (3) the centrifugal flow of bile (small arrows) fo fhe small bile duct in the portal space. (Reproduced from Bloom W and Fawcett DW (eds.) (1968) A Textbook of Histology, 9th edn. Philadelphia Saunders redrawn and modified from Ham, Textbook of Histology. Philadelphia Lippincott, with permission from Lippincott.)...

GLD is more concentrated in the central areas of the liver lobules than in the periportal zones. This pattern of distribution is the reverse of that of ALT. Pronounced release of GLD is therefore to be expected in conditions in which cen-trilobular necrosis occurs (e.g., as a result of ischemia or in halothane toxicity). 

Figure 47-2 A low-magnification scanning electron micrograph depicting a portion of a liver lobule from a rat liver. CVJ Central vein PV, porta vein PLV, perilobular venules. fFrom Zakim 0, Boyer TD. Hepatology A textbook of liver disease, 3rd ed. Philadelphia WB Saunders, 1996 9.)...

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