Refers to shrinkage in cell size or loss of cell substance.
An adaptive response and may result in cell death.
When sufficient number of cells involved in the process the tissue or organ of involvement decreases in size and becomes atrophic.
Can be physiologic or pathologic.
Physiologic atrophy is seen during embryological structural changes and the changes in the uterus after parturition.
Multiple processes are associated with pathologic atrophy and include: atrophy of disuse, as occurs when decreased workload manifests following an injury to an extremity, denervation atrophy, when damage to nerves lead to atrophy of muscle fibers supplied by such nerves, impaired blood supply resulting in ischemia as noted with arterial occlusive disease or brain atrophy, inadequate nutrition such as muscle wasting of cachexia and protein malnutrition, loss of endocrine stimulation as noted with breast atrophy, menopausal atrophy of the endometrium, aging, with loss of brain and muscle cell loss and pressure related, as seen with compression of surrounding tissues by an enlarged benign lesion.
Cells undergoing atrophy have a decrease in structural components with decreased function and can lead eventually to cell death.
Increased protein degradation plays a role.