Structures of the ISL and ISHC. A) An ISL Sinusoid Segment. The Sinusoid Segment is the functional unit of the ISL. It contains thousands of Hepatocytes and Endothelial Cells contained within distinct spaces. B) Simplified component diagram of a Hepatocyte. Only PMMs are shown, highlighting the fact that the ISL and ISHC share the same PMMs. BindingHandler is grayed to emphasize that it belongs to the Cell class, from which Hepatocyte derives. C) ISHC structure. The ISHC contains two grids: CellSpace and MediaSpace (only portions of each grid are shown). Drugs can move laterally within a grid, or between CellSpace and MediaSpace, subject to the parameters pExitMedia and pExitCell.