Liver units in three dimensions: I. organization of argyrophilic connective tissue skeleton in porcine Liver with particular reference to the “compound hepatic lobule”

Abstract

Liver units were investigated in pig livers by means of histologic serial tracing, physical model building, and computer-aided three-dimensional imaging. Observations of the argyrophilic connective tissue skeleton were based mainly on the celloidin-embedded serial sections treated with silver impregnation. The parenchymal mass that clothed the initial segments of hepatic venous radicles was demarcated by fibrous septa which formed isolable units with two basic patterns: the simple hepatic lobule (SHL) and the compound hepatic lobule (CHL). Both lobule types presented regular limiting structures circumscribing each unit. Three-dimensional studies revealed that 25% of the lobules in a section belonged to the SHL type and 75% to the CHL type, the latter being predominant among the surface lobules. When considered in only two dimensions, however, the SHL-like lobules constituted the majority. Polygonal analysis disclosed that the pentagonal lobule was the most typical, instead of the "hexagonal" or "classic" lobule. The CHLs represented a multiaxial unit containing a system of venous tributaries in accordance with intralobular septation, whereas the SHLs were found with one axial vessel having a dendritic tendency at the incipient end; some SHLs were drained eccentrically by separate vessels into a sublobular vein. It was observed that, in dividing CHLs, whereas particular sinosoids were transformed into portal twigs, other sinusoids were changed into central venous tributaries. Fibrous deposition occurred along the septal-line sinusoids, bringing into view the septum-initiating plane. Fibroconnective tissue was supplied from the portal area and central (sublobular) adventitia, where portal triad structures and adventitial arterioles, respectively, were included. The findings of the present study facilitate the understanding of several characters of the lobules that have been reported previously, or occasionally postulated, such as the portal-central bridging tendency, the intralobular arterioles or ductules, the translobular artery or portal vein, the "portal-portal" or "portal-central" anastomoses, and the apposition of pericentral zone close to periportal zone. Based on differences in argyrophilia of sinusoidal reticulum, in proportion of lobule types, and in vasculature, the anatomic heterogeneity of liver unit was demonstrable in zonality, regionality, and locality.

Hydrodynamic gene delivery to the pig liver via an isolated segment of the inferior vena cava

“…The fundamental problem might be the larger size of the pig liver, in which case clinical application will need to take this unavoidable factor into account. However, the pig liver is known to have an unusual connective tissue framework, with a distinct collagen lattice around each hepatic lobule, 19 a characteristic not seen in rodents or man. If this is the fundamental problem, then our study and other studies [15][16][17] in pigs might underestimate the effectiveness of the hydrodynamic procedure in man.…”

The portal lobule in rat liver fibrosis: A re-evaluation of the liver unit

“…Complex CVs are comprised of the hepatic vein together with many small branches connected directly with sinusoids. In human 29 and pig 30 livers, sinusoids enter only the smallest branches of hepatic veins. In addition, CVs in the rat (Figs.…”

The isolated artery: An intrahepatic arterial pathway that can bypass the lobular parenchyma in mammalian livers

“…Intrahepatic termination of the arteria hepatica propria has been a controversial issue for more than a century. 1 Review of the literature shows that the subject became controversial in 1866, when Chrzonszczewsky, 2 with his classic experiments of selective ligation and injection, observed that branches of the hepatic artery penetrated into the depth of the lobule, and concluded subsequently that the artery nourished the central half of the liver lobule, whereas the portal vein supplied the peripheral half. One hundred years later, in 1966, not only were the statements unsupported, but also many studies extended the controversy about the anatomy [3][4][5][6][7] and physiology 8,9 of intrahepatic arterial distribution.…”