英语翻译Throughouthistorymanhashadtoacceptthefactthatalllivingthingsmustdie.Butpeoplenowlivelongerthantheyusedto.Yet,alllivingthingsstillshowtheeffectofaging,whichwilleventuallyresultindeaths.,thebodyandthe
英语翻译
Throughouthistorymanhashadtoacceptthefactthatalllivingthingsmustdie.Butpeoplenowlivelongerthantheyusedto.Yet,alllivingthingsstillshowtheeffectofaging,whichwilleventuallyresultindeaths.,thebodyandtheorganstheyformdonotfunctionaswellastheydidinchildhoodandteenageyears.Thebodyprovideslessprotectionagainstdiseaseandismorepronetoaccident.
Anumberofrelatedcausesmaycontributetoaging.Somecellsofthebodyhaveafairlylonglife,buttheyarenotreplacedwhentheydie.Asapersonages,thenumberofbraincellsandmuscle（肌肉）cellsdecreases.Otherbodycellsdieandarereplacedbynewcells.Inanagingpersonthenewcellsmaynotbeasworkableorascapableofgrowthasthoseofayoungperson.
Anotherfactorinagingmaybechangeswithinthecellsthemselves.Someoftheproteinchemicalsincellsareknowntochangewithageandbecomelesselastic（有弹性的）.Thisiswhytheskinofoldpeoplewrinkles（皱纹）andhangsloose.Thisisalsothereasonwhyoldpeopleshrinkinheight.Theremaybeothermoreimportantchemicalchangesinthecells.Somecomplexcellchemicals,suchasDNAanRNA,storeandpassoninformationthatthecellsneed.Agingmayaffectthisprocessandchangetheinformation-carryingmoleculessothattheydonottransmittheinformationaswell.