ABSTRACT
This chapter considers the functions and lifestyles of the specialized cells in the adult body of a vertebrate. It describes how cells work together to perform their tasks, how new specialized cells are born, how they live and die, and how the architecture of tissues is preserved despite the constant replacement of old cells by new. The chapter examines in particular the role played in many tissues by stem cells cells that are specialized to provide an indefinite supply of fresh differentiated cells where these are lost, discarded, or needed in greater numbers. It discusses these topics through a series of examples some chosen because they illustrate important general principles, others because they highlight favorite objects of study, still others because they pose intriguing problems that cell biology has yet to solve. Cells evolved originally as free-living individuals, but the cells that matter most to us, as human beings, are specialized members of a multicellular community.
