ABSTRACT
The growth, development, and maintenance of multicellular organisms depend not only on production of cells but also on mechanisms to destroy them. The maintenance of tissue size requires that cells die at the same rate as they are produced. In contrast to apoptosis, animal cells that die in response to an acute insult, such as trauma or a lack of blood supply, usually do so by a process called cell necrosis. This chapter focuses on the major functions of apoptosis, its mechanism and regulation, and how excessive or insufficient apoptosis can contribute to human disease. The amount of apoptotic cell death that occurs in developing and adult animal tissues is astonishing. In the developing vertebrate nervous system more than half of many types of nerve cells normally die soon after they are formed. In adult tissues that are neither growing nor shrinking, cell death and cell division must be tightly regulated to ensure that they are exactly in balance.
