Cellular Adaptation I: Introduction and Atrophy

Cells adapt to physiological demands or pathological stress by adjusting their size, number, or function.

Major forms of cellular adaptation include atrophy, hypertrophy, hyperplasia, and metaplasia.

Atrophy involves a reduction in cell size and, in some tissues, a reduction in cell number, often leading to tissue or organ shrinkage. Commonly affected organs include skeletal muscle, the brain, the heart, and reproductive tissues.

Physiological atrophy develops naturally with aging, such as the shrinking of the thymus after childhood.

Pathological atrophy often develops in response to chronic disease or prolonged stress.

For example, brain atrophy may result from conditions such as chronic cerebral ischemia and is often associated with atherosclerosis.

Atrophic cells contain fewer organelles, such as mitochondria and rough endoplasmic reticulum, which reduces overall metabolic activity.

Additionally, autophagy, a process in which cells degrade internal components, contributes to atrophy, especially during nutrient deprivation or stress.