大学英语六级考试阅读：背诵美文(7)
<p> <span word="Muscles">Muscles</span> <span word="and">and</span> <span word="Human">Human</span> <span word="Body">Body</span></p><p> <span word="It">It</span> <span word="is">is</span> <span word="in">in</span> <span word="the">the</span> <span word="joints">joints</span> <span word="of">of</span> <span word="the">the</span> <span word="human">human</span> <span word="body">body</span> <span word="that">that</span> <span word="movements">movements</span> <span word="of">of</span> <span word="the">the</span> <span word="bones">bones</span> <span word="take">take</span> <span word="place">place</span>. <span word="The">The</span> <span word="movement">movement</span> <span word="itself">itself</span> <span word="is">is</span> <span word="caused">caused</span> <span word="by">by</span> <span word="the">the</span> <span word="pull">pull</span> <span word="of">of</span> <span word="sheets">sheets</span> <span word="and">and</span> <span word="cords">cords</span> <span word="of">of</span> <span word="very">very</span> <span word="tough">tough</span> <span word="tissue">tissue</span> <span word="called">called</span> <span word="muscle">muscle</span>. <span word="Muscle">Muscle</span> <span word="tissue">tissue</span> <span word="has">has</span> <span word="the">the</span> <span word="special">special</span> <span word="ability">ability</span> <span word="to">to</span> <span word="shorten">shorten</span> <span word="itself">itself</span> <span word="so">so</span> <span word="that">that</span> <span word="the">the</span> <span word="bone">bone</span> <span word="on">on</span> <span word="which">which</span> <span word="it">it</span> <span word="pulls">pulls</span> <span word="has">has</span> <span word="to">to</span> <span word="move">move</span>. <span word="When">When</span> <span word="muscle">muscle</span> <span word="tissue">tissue</span> <span word="shortens">shortens</span>, <span word="it">it</span> <span word="also">also</span> <span word="bunches">bunches</span> <span word="up">up</span>. <span word="Muscle">Muscle</span> <span word="tissue">tissue</span> <span word="covers">covers</span> <span word="the">the</span> <span word="body">body</span> <span word="in">in</span> <span word="sheets">sheets</span> <span word="and">and</span> <span word="bands">bands</span> <span word="that">that</span> <span word="lie">lie</span> <span word="between">between</span> <span word="the">the</span> <span word="skin">skin</span> <span word="and">and</span> <span word="the">the</span> <span word="skeleton">skeleton</span>. <span word="The">The</span> <span word="bones">bones</span> <span word="are">are</span> <span word="the">the</span> <span word="framework">framework</span> <span word="of">of</span> <span word="the">the</span> <span word="body">body</span>, <span word="but">but</span> <span word="the">the</span> <span word="muscles">muscles</span> <span word="fill">fill</span> <span word="out">out</span> <span word="the">the</span> <span word="body">body</span> <span word="shape">shape</span>. <span word="Most">Most</span> <span word="muscles">muscles</span> <span word="extend">extend</span> <span word="from">from</span> <span word="one">one</span> <span word="bone">bone</span> <span word="to">to</span> <span word="another">another</span>. <span word="When">When</span> <span word="the">the</span> <span word="muscle">muscle</span> <span word="between">between</span> <span word="the">the</span> <span word="bones">bones</span> <span word="shortens">shortens</span>, <span word="one">one</span> <span word="bone">bone</span> <span word="has">has</span> <span word="to">to</span> <span word="move">move</span>. <span word="The">The</span> <span word="point">point</span> <span word="where">where</span> <span word="the">the</span> <span word="muscle">muscle</span> <span word="is">is</span> <span word="fastened">fastened</span> <span word="to">to</span> <span word="the">the</span> <span word="unmoving">unmoving</span> <span word="bone">bone</span> <span word="is">is</span> <span word="called">called</span> <span word="the">the</span> <span word="origin">origin</span> <span word="of">of</span> <span word="the">the</span> <span word="muscle">muscle</span>, <span word="whereas">whereas</span> <span word="the">the</span> <span word="point">point</span> <span word="where">where</span> <span word="the">the</span> <span word="muscle">muscle</span> <span word="is">is</span> <span word="not">not</span> <span word="fastened">fastened</span> <span word="to">to</span> <span word="the">the</span> <span word="bone">bone</span> <span word="that">that</span> <span word="is">is</span> <span word="to">to</span> <span word="be">be</span> <span word="moved">moved</span> <span word="is">is</span> <span word="called">called</span> <span word="the">the</span> <span word="insertion">insertion</span>. <span word="Sometimes">Sometimes</span> <span word="the">the</span> <span word="muscle">muscle</span> <span word="is">is</span> <span word="not">not</span> <span word="attached">attached</span> <span word="directly">directly</span> <span word="to">to</span> <span word="the">the</span> <span word="bone">bone</span> <span word="but">but</span> <span word="to">to</span> <span word="a">a</span> <span word="tough">tough</span>, <span word="nonstretchable">nonstretchable</span> <span word="cord">cord</span>, <span word="or">or</span> <span word="tendon">tendon</span>, <span word="that">that</span> <span word="is">is</span> <span word="attached">attached</span> <span word="to">to</span> <span word="the">the</span> <span word="bone">bone</span>. <span word="Muscles">Muscles</span> <span word="do">do</span> <span word="not">not</span> <span word="push">push</span>; <span word="they">they</span> <span word="can">can</span> <span word="only">only</span> <span word="pull">pull</span>. <span word="To">To</span> <span word="bend">bend</span> <span word="the">the</span> <span word="arm">arm</span> <span word="at">at</span> <span word="the">the</span> <span word="elbow">elbow</span>, <span word="the">the</span> <span word="muscle">muscle</span> <span word="at">at</span> <span word="the">the</span> <span word="front">front</span> <span word="of">of</span> <span word="the">the</span> <span word="upper">upper</span> <span word="arm">arm</span> <span word="has">has</span> <span word="to">to</span> <span word="shorten">shorten</span> <span word="and">and</span> <span word="bunch">bunch</span> <span word="up">up</span>. <span word="To">To</span> <span word="unbend">unbend</span> <span word="the">the</span> <span word="arm">arm</span> <span word="other">other</span> <span word="muscles">muscles</span> <span word="in">in</span> <span word="the">the</span> <span word="back">back</span> <span word="of">of</span> <span word="the">the</span> <span word="arm">arm</span> <span word="have">have</span> <span word="to">to</span> <span word="shorten">shorten</span>. <span word="These">These</span> <span word="two">two</span> <span word="sets">sets</span> <span word="of">of</span> <span word="muscles">muscles</span> - <span word="the">the</span> <span word="front">front</span> <span word="and">and</span> <span word="the">the</span> <span word="back">back</span> - <span word="are">are</span> <span word="said">said</span> <span word="to">to</span> <span word="act">act</span> <span word="in">in</span> <span word="opposition">opposition</span> <span word="to">to</span> <span word="each">each</span> <span word="other">other</span>. <span word="When">When</span> <span word="one">one</span> <span word="set">set</span> <span word="is">is</span> <span word="working">working</span>, <span word="the">the</span> <span word="other">other</span> <span word="set">set</span> <span word="is">is</span> <span word="usually">usually</span> <span word="relaxed">relaxed</span>. <span word="But">But</span> <span word="there">there</span> <span word="are">are</span> <span word="times">times</span> <span word="when">when</span> <span word="both">both</span> <span word="of">of</span> <span word="them">them</span> <span word="work">work</span>. <span word="Sometimes">Sometimes</span> <span word="muscles">muscles</span> <span word="are">are</span> <span word="called">called</span> <span word="upon">upon</span> <span word="to">to</span> <span word="do">do</span> <span word="more">more</span> <span word="than">than</span> <span word="simply">simply</span> <span word="pull">pull</span> <span word="in">in</span> <span word="one">one</span> <span word="direction">direction</span>. <span word="They">They</span> <span word="may">may</span> <span word="have">have</span> <span word="to">to</span> <span word="perform">perform</span> <span word="a">a</span> <span word="turning">turning</span> <span word="motion">motion</span>. <span word="To">To</span> <span word="be">be</span> <span word="able">able</span> <span word="to">to</span> <span word="do">do</span> <span word="this">this</span>, <span word="the">the</span> <span word="muscle">muscle</span> <span word="must">must</span> <span word="be">be</span> <span word="attached">attached</span> <span word="to">to</span> <span word="the">the</span> <span word="bone">bone</span> <span word="at">at</span> <span word="an">an</span> <span word="angle">angle</span>. <span word="By">By</span> <span word="pulling">pulling</span>, <span word="the">the</span> <span word="muscle">muscle</span> <span word="can">can</span> <span word="cause">cause</span> <span word="the">the</span> <span word="bone">bone</span> <span word="to">to</span> <span word="pivot">pivot</span>. <span word="A">A</span> <span word="few">few</span> <span word="muscles">muscles</span> <span word="have">have</span> <span word="special">special</span> <span word="functions">functions</span>. <span word="The">The</span> <span word="diaphragm">diaphragm</span>, <span word="for">for</span> <span word="example">example</span>, <span word="forces">forces</span> <span word="the">the</span> <span word="lungs">lungs</span> <span word="to">to</span> <span word="take">take</span> <span word="in">in</span> <span word="air">air</span>. <span word="This">This</span> <span word="part">part</span> <span word="of">of</span> <span word="breathing">breathing</span> <span word="is">is</span> <span word="not">not</span> <span word="primarily">primarily</span> <span word="a">a</span> <span word="bone">bone</span> <span word="moving">moving</span> <span word="operation">operation</span>.</p>
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