Atrophy
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atrophy definition pathology cellular adaptation site:nih.gov OR site:ncbi.nlm.nih.gov
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atrophy pathology
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Atrophy is a decrease in the size of an organ or tissue caused by reduced cell size, and sometimes reduced cell number.
Causes
- Disuse: muscle wasting after bed rest or immobilization in a cast
- Denervation: loss of nerve supply to muscle
- Reduced blood supply: chronic ischemia
- Malnutrition or chronic illness: for example cancer cachexia
- Loss of hormonal stimulation: endometrial and breast atrophy after menopause
- Pressure: compression of tissue by a mass
Types
- Physiological atrophy: normal developmental or age-related change, such as involution of the thymus or post-menopausal reproductive tissue changes.
- Pathological atrophy: occurs due to disease, disuse, nerve injury, inadequate nutrition, or impaired blood supply.
Cellular mechanism
Cells adapt by decreasing protein synthesis and increasing protein breakdown, mainly via the ubiquitin-proteasome pathway. Autophagy may also remove cellular organelles. Early disuse atrophy can be reversible if normal stimulation returns.
Robbins, Cotran & Kumar Pathologic Basis of Disease, p. 71.
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