Atrophy

Atrophy is the partial or complete wasting away of a part of the body, representing a reduction in the size of cells, organs, or tissues after they have reached normal mature growth. Causes include gene mutations that impair an organ's structure, poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the affected tissue, excessive cell death through apoptosis, and disuse or lack of exercise. Disuse atrophy results from prolonged immobility such as extended bedrest or a cast, and is usually reversible with exercise unless severe. Pathological atrophy arises from disease or loss of trophic support and includes cachexia associated with cancer or AIDS, age related sarcopenia, and various motor neuron diseases. Neurogenic atrophy is caused by diseases affecting the motor nerves, including Charcot-Marie-Tooth disease, poliomyelitis, amyotrophic lateral sclerosis, and Guillain-Barre syndrome. Some atrophy is a normal part of development, such as involution of the thymus in childhood and shrinkage of the tonsils in adolescence.