Aging is the process of growing old.It occurs eventually in every living thing provided,of course,that an illness or accident does not kill it prematurely.The most familiar outward signs of aging may be seen in old people,such as the garay ing of the hair and the wringkling of the skin.Signs of aging in a pet dog or cat include loss of energy ,a decline in hearing and eyesight,or even a slight graying of the coat.Plants age too,but the signs are much harder to detect.
Most body parts grow bigger and stronger, and function more efficiently during childhood.They reach theri peak at the time of maturity, or early adulthood.After that ,they begin to decline. Bones,for example,gradually become lighter and more brittle.In the aged,the joints between the bones also become tigid and more inflexible. This can make moving very painful.
All the major organs of the body show signs of aging.The brain,for example,works less efficiently,and even gets smaller in size.Thinking process of all sorts are slowed down.Old people often have trouble in remembering the recent events.One of the most serious changes of old age occurs in the arteries, the blood vessels that lead from the heart.They become thickened and constricted,allowing less blood to flow to the rest of the body.This condition caccounts,directly or indirectly,for many of the diseases of the aged.It may ,for example,result in heart attack.
Aging is not a uniform process.Different parts of the body wear out at different rates.There are great differences among people in their rate of aging.Even the cells of the body differ in the way they age.The majority of cells are capable of reproducing themselves many times during the course of a lifetime. Nerve cells and muscle fibers can never be replaced once they wear out.
Gerontologists - scientists who study the process of aging -believe the wearing out of the body is controlled by a build-in biological time-clock.They are trying to discover how this clock works so that they can slow down the process.This could give man a longer life and more productive years.
关键字:英语文库
生词表:
Most body parts grow bigger and stronger, and function more efficiently during childhood.They reach theri peak at the time of maturity, or early adulthood.After that ,they begin to decline. Bones,for example,gradually become lighter and more brittle.In the aged,the joints between the bones also become tigid and more inflexible. This can make moving very painful.
All the major organs of the body show signs of aging.The brain,for example,works less efficiently,and even gets smaller in size.Thinking process of all sorts are slowed down.Old people often have trouble in remembering the recent events.One of the most serious changes of old age occurs in the arteries, the blood vessels that lead from the heart.They become thickened and constricted,allowing less blood to flow to the rest of the body.This condition caccounts,directly or indirectly,for many of the diseases of the aged.It may ,for example,result in heart attack.
Aging is not a uniform process.Different parts of the body wear out at different rates.There are great differences among people in their rate of aging.Even the cells of the body differ in the way they age.The majority of cells are capable of reproducing themselves many times during the course of a lifetime. Nerve cells and muscle fibers can never be replaced once they wear out.
Gerontologists - scientists who study the process of aging -believe the wearing out of the body is controlled by a build-in biological time-clock.They are trying to discover how this clock works so that they can slow down the process.This could give man a longer life and more productive years.
关键字:英语文库
生词表:
- eventually [i´ventʃuəli]
ad.最后，终于 四级词汇 - efficiently [i´fiʃəntli] ad.有效地；能胜任地 六级词汇
- maturity [mə´tjuəriti] n.成熟；完备 四级词汇
- biological [,baiə´lɔdʒikəl] a.生物学(上)的 六级词汇
- trying [´traiiŋ] a.难堪的；费劲的 四级词汇
京公网安备 11011202003401号
