Atrophy: Wikis

  
  

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

Encyclopedia

From Wikipedia, the free encyclopedia

Atrophy
Classification and external resources

Mouse with spinal muscular atrophy
MeSH D001284

Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the genetic to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself. Hormonal and nerve inputs that maintain an organ or body part are referred to as trophic [noun] in medical practice. Trophic describes the trophic condition of tissue. A diminished muscular trophic is designated as atrophy.

Atrophy is a general physiological process of reabsorption and breakdown of tissues, involving apoptosis on a cellular level. When it occurs as a result of disease or loss of trophic support due to other disease, it is termed pathological atrophy, although it can be a part of normal body development and homeostasis as well.

Contents

Atrophy examples

Normal development

Examples of atrophy as part of normal development include shrinking and involution of the thymus in early childhood and the tonsils in adolescence.

Muscle atrophies

Disuse atrophy of muscles (muscle atrophy) and bones, with loss of mass and strength, can occur after prolonged immobility, such as extended bedrest, or having a body part in a cast (living in darkness for the eye, bedridden for the legs etc.). This type of atrophy can usually be reversed with exercise unless severe. Astronauts in microgravity must exercise regularly to minimize atrophy of their limb muscles.

There are many diseases and conditions which cause atrophy of muscle mass. For example diseases such as cancer and AIDS induce a body wasting syndrome called "cachexia", which is notable for the severe muscle atrophy seen. Other syndromes or conditions which can induce skeletal muscle atrophy are congestive heart failure and liver disease.

During aging, there is a gradual decrease in the ability to maintain skeletal muscle function and mass. This condition is called "sarcopenia", and may be distinct from atrophy in its pathophysiology. While the exact cause of sarcopenia is unknown, it may be induced by a combination of a gradual failure in the "satellite cells" which help to regenerate skeletal muscle fibers, and a decrease in sensitivity to or the availability of critical secreted growth factors which are necessary to maintain muscle mass and satellite cell survival.[1]

Dystrophies, myosities, and motor neuron conditions

Pathologic atrophy of muscles can occur due to diseases of the motor nerves, or due to diseases of the muscle tissue itself. Examples of atrophying nerve diseases include CMT (Charcot Marie Tooth syndrome) poliomyelitis, amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease), and Guillain-Barré syndrome. Examples of atrophying muscle diseases include muscular dystrophy, myotonia congenita, and myotonic dystrophy.

Changes in Na+ channel isoform expression and spontaneous activity in muscle called fibrillation can also result in muscle atrophy.

Gland atrophy

The adrenal glands atrophy during prolonged use of exogenous glucocorticoids like prednisone. Atrophy of the breasts can occur with prolonged estrogen reduction, as with anorexia nervosa or menopause. Atrophy of the testes occurs with prolonged use of enough exogenous sex steroid (either androgen or estrogen) to reduce gonadotropin secretion.

Vaginal atrophy

In post-menopausal women, the walls of the vagina become thinner. The mechanism for the age-related condition is not yet clear, though there are theories that the effect is caused by decreases in estrogen levels.[2] This atrophy, and that of the breasts concurrently, is consistent with the homeostatic (normal development) role of atrophy in general, as after menopause the body has no further functional biological need to maintain the reproductive system which it has permanently shut down.

Research

It has been reported that some drugs might prevent the loss of the muscle wasting that occurs in immobile, bedridden patients.[3] Testing upon mice showed that it blocked the activity of a protein present in the muscle that is involved in muscle atrophy.[4] However the concerns for the drug's longterm effects on the heart preclude its routine use in humans for this indication, and further alternative drugs are being sought.[3] Not exercising is the main cause for muscle atrophy.

See also

Stanley Eitzen's: the Atrophy of Social Life

References

  1. ^ Campellone, Joseph V. (2007-05-22). "Muscle atrophy" (html). MedlinePlus. http://www.nlm.nih.gov/medlineplus/ency/article/003188.htm. Retrieved 2007-10-02. 
  2. ^ "Types of Atrophy" (html). http://medicine.science-tips.org/health/diseases-and-conditions/types-of-atrophy.html. Retrieved 2007-10-02. 
  3. ^ a b "Drug could stop muscle wasting'". NetDoctor.co.uk. 2006-05-25. http://www2.netdoctor.co.uk/news/index.asp?y=2006&m=5&d=25&id=123026. Retrieved 2006-05-27. 
  4. ^ Wang X, Hockerman GH, Green Iii HW, Babbs CF, Mohammad SI, Gerrard D, Latour MA, London B, Hannon KM, Pond AL (May24 2006). "Merg1a K+ channel induces skeletal muscle atrophy by activating the ubiquitin proteasome pathway". FASEB J 20: 1531. doi:10.1096/fj.05-5350fje. PMID 16723379. 

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

Medical warning!
This article is from the 1911 Encyclopaedia Britannica. Medical science has made many leaps forward since it has been written. This is not a site for medical advice, when you need information on a medical condition, consult a professional instead.

ATROPHY (Gr. apriv., Tpocin), nourishment), a term in medicine used to describe a state of wasting due to some interference with the function of healthy nutrition (see Pathology). In the living organism there are always at work changes involving the waste of its component tissues, which render necessary, in order to maintain and preserve life, the supply and proper assimilation of nutritive material. It is also essential for the maintenance of health that a due relation exist between these processes of waste and repair, so that the one may not be in excess of the other. When the appropriation of nutriment exceeds the waste, hypertrophy or increase in bulk of the tissues takes place. When, on the other hand, the supply of nutritive matter is suspended or diminished, or when the power of assimilation is impaired, atrophy or wasting is the result. Thus the whole body becomes atrophied in many diseases; and in old age every part of the frame, with the single exception of the heart, undergoes atrophic change. Atrophy may, however, affect single organs or parts of the body, irrespective of the general state of nutrition, and this may be brought about in a variety of ways. One of the most frequently observed of such instances is atrophy from disuse, or cessation of function. Thus, when a limb is deprived of the natural power of motion, either by paralysis or by painful joint disease, the condition of exercise essential to its nutrition being no longer fulfilled, atrophy of all its textures sooner or later takes place., The brain in imbeciles is frequently observed to be shrivelled, and in many cases of blindness there is atrophy of the optic nerve and optic tract. This form of atrophy is likewise well exemplified in the case of those organs and structures of the body which subserve important ends during foetal life, but which, ceasing to be necessary after birth, undergo a sort of natural atrophy, such as the thymus gland, and certain vessels specially concerned in the foetal circulation. The uterus after parturition undergoes a certain amount of atrophy, and the ovaries, after the child-bearing period, become shrunken. Atrophy of a part may also be caused by interruption to its normal blood-supply, as in the case of the ligature or obstruction of an artery. Again, long-standing disease, by affecting the nutrition of an organ and by inducing the deposit of morbid products, may result in atrophy, as frequently happens in affections of the liver and kidneys. Parts that are subjected to continuous pressure are liable to become atrophied, as is sometimes seen in internal organs which have been pressed upon by tumours or other morbid growths, and is well illustrated in the Chinese practice of foot-binding. Atrophy may manifest itself simply by loss of substance; but, on the other hand, it is often found to co-exist with degenerative changes in the textures affected and the formation of adventitious growth, so that the part may not be reduced in bulk although atrophied as regards its proper structure. Thus, in the case of the heart, when affected with fatty degeneration, there is atrophy of the proper muscular texture, but as this is largely replaced by fatty matter, the organ may undergo no diminution in volume, but may, on the contrary, be increased in size. Atrophy is usually a gradual and slow process, but sometimes it proceeds rapidly. In the disease known by the name of acute yellow atrophy of the liver, that organ undergoes such rapidly destructive change as results in its shrinking to half, or one-third, of its normal size in the course of a few days. The term progressive muscular atrophy (synonyms, wasting or creeping palsy) is applied to an affection of the muscular system, which is characterized by the atrophy and subsequent paralysis of certain muscles, or groups of muscles, and is associated with morbid changes in the anterior roots of the nerves of the spinal cord. This disease begins insidiously, and is often first observed to affect the muscles of one hand, generally the right. The attention of the sufferer is first attracted by the power of the hand becoming weakened, and then there is found to be a wasting of certain of its muscles, particularly those of the ball of the thumb. Gradually other muscles in the arms and legs become affected in a similar manner, their atrophy being attended with a corresponding diminution in power. Although sometimes arrested, this disease tends to progress, until in course of time the greater part of the muscular system is implicated and a fatal result ensues.


<< Atrium

Atropos >>








Got something to say? Make a comment.
Your name
Your email address
Message