Cellular adaptation

Morphological adaptations observed at the cellular level include atrophy, hypertrophy, hyperplasia, and metaplasia.

For example, adipocytes (fat cells) may expand in size by depositing more lipid within cytoplasmic vesicles.

An example of physiologic hypertrophy is in skeletal muscle with sustained weight bearing exercise.

It occurs to a lesser extent in bone, cartilage, and smooth muscle cells.

Stem cells are found in epithelia and embryonic mesenchyme of connective tissue.

A prominent example of metaplasia involves the changes associated with the respiratory tract in response to inhalation of irritants, such as smog or smoke.

These transformed cells may become dysplastic or cancerous if the stimulus (e.g., cigarette smoking) is not removed.

[8] Dysplasia refers to abnormal changes in cellular shape, size, and/or organization.

Illustration of adipocytes of different sizes. In response to dietary excess energy intake, adipocytes adapt by increased storage of lipids, resulting in cellular hypertrophy.