What is the term used for the increase in the number of cells in tissues?

The term that refers to an increase in the number of cells in tissues is hyperplasia. This process occurs when there is a demand for more cells, such as during tissue growth, repair, or in response to certain physiological stimuli. Hyperplasia can be a normal response, such as the proliferation of liver cells after injury or the increase in breast tissue during pregnancy.

In contrast, atrophy describes the decrease in the size or number of cells, leading to reduced tissue mass. Hypertrophy involves an increase in cell size rather than cell number, as seen in muscle tissues that adapt to increased workloads. Dysplasia refers to abnormal development or growth of cells, which may indicate early changes that could lead to cancer. Each of these terms has specific implications in the context of tissue response and pathology, but hyperplasia directly addresses the question of increased cell numbers.