ABSTRACT
This chapter illustrates some of the diversity of specialized cell types and observes how they work together to perform their tasks. It examines in particular the role played in many tissues by stem cells—cells that are specialized to provide a fresh supply of differentiated cells where these need to be continually replaced or regenerated. The chapter discusses how stem cells is generated and manipulated artificially, and confronts the practical question that underlies the current storm of interest in stem-cell technology. It explains how one can understand the processes of cell differentiation and tissue renewal to improve upon nature, and make good those injuries and failings of the human body that have hitherto seemed to be beyond repair. Many tissues in the adult mammalian body are continually renewed by stem cells. The lining of the gut renews itself more rapidly than any other tissue in the mammalian body and provides a paradigm for the workings of stem-cell systems.
