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Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, excessive amount of apoptosis of cells, and disuse or lack of exercise or disease intrinsic to the tissue itself.
Cerebral atrophy is a common feature of many of the diseases that affect the brain. [1] Atrophy of any tissue means a decrement in the size of the cell, which can be due to progressive loss of cytoplasmic proteins. In brain tissue, atrophy describes a loss of neurons and the connections between them.
[4] [5] Intentional denervation is a valuable surgical technique for managing some medical conditions, such as renal denervation in the setting of uncontrolled hypertension. [6] Pathological denervation, by contrast, is associated with serious health sequelae , including increased infection susceptibility and tissue dysfunction.
Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness and causes disability.
(Atrophy, the wasting away of already existing cells, is technically the direct opposite of both hyperplasia and hypertrophy.) Hypoplasia can be present in any tissue or organ. It is descriptive of many medical conditions, including underdevelopment of organs such as: Breasts during puberty; Testes in Klinefelter's syndrome
These terms were discontinued by consensus in 1996 and replaced with MSA and its subtypes, [60] but awareness of these older terms and their definitions is helpful to understanding the relevant literature prior to 1996. These include striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA), and Shy–Drager syndrome. [61]
Upon atrophy, the size and activity are dramatically reduced, and the organ is primarily replaced with fat. The atrophy is due to the increased circulating level of sex hormones , and chemical or physical castration of an adult results in the thymus increasing in size and activity.
The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons. The prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS) and the 10-year survival rate to be 12% (vs 6% in ALS).