ABSTRACT
Cells are generally able to cope with a range of normal physiological demands, a state referred to as homeostasis. When fluctuations in the environment around the cell are more severe, leading to cellular stress, a number of adaptive responses may occur. These allow the cell to remain viable but may modify its structure and function. Some of these adaptive responses are characterized by changes in cell size or number.An increase in cell size in response to a stimulus is termed hypertrophy, whereas an increase in the number of cells is called hyperplasia. Atrophy is the process by which there is a decrease in the size of cells in response to a stimulus. Cells may also adapt by changing their differentiation, so-called metaplasia. These phenomena have been considered in Chapter 2 and will also be dealt with in Chapter 5 along with other growth disorders.
