ABSTRACT
Three times the length of the Mississippi River, or 20,000 km, is the extent of hepatocellular tight junctions (TJs) within a human liver if one extrapolates data obtained from rats (Weibel, 1979; Stammler et al., 1990; Hornstein et al., 1992; Rahner et al., 1996). This seal is formed by 200 billion hepatocytes and confines as little as 3.5 cm
of biliary space organized in an anastomosing network of tiny, 1-
µ
m
canaliculi. The secretory surface of the canalicular wall that is formed by the apical membrane domain of hepatocytes totals 115 m
, approximately the size of a fiveroom apartment. It is obvious that stowing these dimensions in a 1500-g organ necessitates an elaborate organization (Figure 27.1A).
