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*Myofibrils removed by disintegration -> sacrolemma too large -> forms folds
*Myofibrils removed by disintegration -> sacrolemma too large -> forms folds
*Caused by:
*Caused by:
**<u>'''Disuse'''</u> (e.g. fracture, failure to use limb, recumbency)
**<u>'''Disuse atrophy'''</u> (e.g. fracture, failure to use limb, recumbency)
***Slower than denervation atrophy
***Slower than denervation atrophy
***Reversible unless too prolonger or severe to cause loss of myofibres
***Reversible unless too prolonger or severe to cause loss of myofibres
**<u>'''Denervation'''</u>
**<u>'''Pressure atrophy'''</u>
***Any prolonged pressure on muscles resulting in muscle atrophy
****Abscesses, neoplasms, parasitic cysts
**<u>'''Denervation atrophy'''</u>
***Any interference or damage to its nerve supply results in muscle atrophy
***Any interference or damage to its nerve supply results in muscle atrophy
****Can be rapid - over 50% of muscle mass may be lost in a few weeks e.g. roarer horses with [[Laryngeal Hemiplegia|laryngeal hemiplegia]]
****Can be rapid - over 50% of muscle mass may be lost in a few weeks e.g. roarer horses with [[Laryngeal Hemiplegia|laryngeal hemiplegia]]
***Sometimes replaced by fat tissue -> increased size of muscle = ''pseudohypertrophy''
***Sometimes replaced by fat tissue -> increased size of muscle = ''pseudohypertrophy''
***Muscle may have a mixture of atrophied and [[Muscle Hypertrophy|hypertrophied]] (due to increased work load) fibres if some motor units are not damaged
***Muscle may have a mixture of atrophied and [[Muscle Hypertrophy|hypertrophied]] (due to increased work load) fibres if some motor units are not damaged
**<u>'''Metabolisation of muscle protein'''</u> for nutrients during:
**<u>'''Nutritional atrophy'''</u> for nutrients during:
***Malnutrition, cachexia, senility
***Malnutrition, cachexia, senility
***Gradual onset except for some febrile diseases causing cachexia
***Gradual onset except for some febrile diseases causing cachexia
***Grossly:
***Grossly:
****Smaller, darker, thinner muscles
****Smaller, darker, thinner muscles
***<u>'''Senile atrophy'''</u>
****Similar to nutritional atrophy.
****Lipofuscin pigmentation is common
*****Grossly:
******Yellow-brown / dark brown colour (esp in diaphragm)
[[Category:Muscles - Degenerative Pathology]]
[[Category:Muscles - Degenerative Pathology]]