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★中国招生考试网 http://www.chinazhaokao.com)英语听力频道为大家整理的普特英语听力材料推荐：静脉血管的秘密，供大家参考。更多阅读请查看本站英语听力频道。Oy Veins!
Veins are pretty important. After all, they carry blood from various parts of the body to the heart. But for all their significance, veins are modest, too. Yours are probably content to work behind the scenes, tucked away beneath the skin.
Twisted And Filled
Sometimes, however, veins take center-stage and become visible as blue lines on the skin, often resembling an unmarked roadmap. If you haven’t guessed by now, we’re talking about varicose veins. Have you ever wondered what are they are and how they form?
Basically, a varicose vein is one that is twisted and filled with backed-up blood. Although they most commonly occur in the legs, varicose veins can also happen in the esophagus, testes and the urinary bladder.
Varicose veins in the legs occur when the valves in a vein near the surface of the skin malfunction.
Faulty Valves
Valves usually keep blood from flowing backwards in the vein once it’s been pumped towards the heart. When the valves don’t work properly, blood gets stuck, causing the vein to swell and kink.
Although varicose veins are usually associated with senior citizens, not every older person has them. Weak valves are often inherited, and can also be caused by wearing clothing that squeezes the legs and veins too tightly.
Varicose veins may seem unsightly, but they’re not usually a cause for major concern. Still, if you have them and want to do something about it, talk to your doctor. Treatments range from wearing strong support stockings to surgery.
噢 血管！
血管相当的重要。毕竟，它们从身体的各个部分向心脏运输血液。虽然血管很重要，但是它们也很谦逊。血管甘愿在幕后工作，在皮肤下默默运输血液。
扭曲的并充满的
然而，有时候血管成为主角，在皮肤上可以看到蓝色的线，很像未被标记的地图。如果你还没有猜到，我们讨论的正是静脉曲张的血管。你是否想知道它们是什么并怎样形成的么？
通常，静脉曲张的血管充满回流的血液并因此扭曲。它们不仅多见于腿部，也会表现在食管、睾丸、膀胱上。
当皮肤表面下的血管的阀门不起作用时，腿上的静脉曲张开始显现。
受损的瓣膜
阀门的作用是防止有心脏送出的血液回流。当阀门不正常工作时，