These concepts, based on 3D reconstructions of serial sections of human (Matsumoto et al., 1979) and rodent liver (Teutsch et al., 1999) describe cone-shaped units observed at the tissue level of organization (branching of portal tracts). In the past 20 years “primary” and “secondary” lobule concepts have also emerged (Matsumoto et al., 1979 Saxena et al., 1999 Teutsch et al., 1999). Rappaport's acinar model of the liver has a physiological rather than morphological basis (emphasizing afferent and efferent sinusoidal flow within the parenchyma), and attempts to describe metabolic variance along a periportal to centrolobular gradient (Jungermann, 1988). For instance, Kiernan's classic lobule is a hexagonal structure with portal tracts at the hexagon corners and a central hepatic venule, whereas Mall's portal lobule places the portal tract as the central axis of the model. While these models share similarities, discrepancies exist in describing hepatobiliary structure/function. histological preparations, electron micrographs) and attempt to characterize the relationship between vasculature, biliary passageways, and the hepatocellular compartment (Kiernan, 1833 Mall, 1906 Elias and Bengelsdorf, 1952 Rappaport, 1958 Fig. The mammalian “classic,” “modified,” and “portal” lobule models describe morphological features encountered in two-dimensional (2D) single sectional views of the liver (e.g. Several conceptual models emerged in the 19th and 20th centuries to describe structure/function relationships of the vertebrate liver lobular mammalian liver models, and a tubular liver model to describe the lower vertebrate livers of birds, fish, reptiles, and amphibians. The in vivo findings presented advance our comparative 3D understanding of vertebrate liver structure/function, help clarify previous discrepancies among vertebrate liver conceptual models, and pose interesting questions regarding the “functional unit” of the vertebrate liver. Our investigations show that hepatobiliary architecture in medaka is based on a polyhedral (hexagonal) structural motif, that the intrahepatic biliary system is an interconnected network of canaliculi and bile-preductules, and that parenchymal architecture in this lower vertebrate is more related to that of the mammalian liver than previously believed. Applying noninvasive in vivo imaging to a living small fish animal model we elucidated, and present here, the 3D architecture of this lower vertebrate liver.
To date, factual information on vertebrate liver architecture in 3 dimensions has remained limited. Understanding three-dimensional (3D) hepatobiliary architecture is fundamental to elucidating structure/function relationships relevant to hepatobiliary metabolism, transport, and toxicity.