Derived from the Greek word meaning ‘a flower losing its petals’, it refers to programmed cell death and replacement. It is a normal biological process in metazoan development that allows the elimination of unwanted cells through activation of the cell death program. The products of apoptosis are absorbed by neighboring cells and by white blood cells called macrophages (see figure below). In contrast to necrosis, which is a form of cell death resulting from acute tissue injury, apoptosis occurs in an ordered process that generally confers advantages during an organism’s life cycle. For example, the differentiation of human fingers requires the cells in between the fingers to initiate apoptosis so that the fingers separate. Abnormal control of apoptosis can have serious consequences, leading to a wide range of diseases, including cancer and schizophrenia.
