Microanatomy of the human liver—exploring the hidden interfaces

The functional unit of an organ may be defined as the smallest, structurally distinct, ‘‘self-sufficient’’ unit that can independently subserve all known functions of that organ. The nephron is exemplary of such a concept, for it is both a well-defined functional and structural unit. A similar hepatic unit that can reconcile the dual vascular supply and the dual outflow tracts (vascular and biliary) with all known liver functions has not been identified. This reflects the functional complexity of the liver and the sophistication of its microarchitectural interfaces. This review addresses the recent resurgence of investigation into the microanatomy of the liver, emphasizes studies in humans, and highlights the ‘‘grey’’ zones in our existing knowledge.