我们附着在一个二氧化碳分子上面,顺着充满泡沫的血液,逐一造访了斯蒂文的心脏和其他身体器官后,直接进入了一条宽阔的管道。再往前,这条管子分成了两支;接着,每条分支再继续分出更窄小的分支,直到分支窄到我们不能挤过去为止。在这里,呼啸而过的气流,发出震耳欲聋的噪音——我们已经进入了斯蒂文的肺部。这个器官像两个海绵袋子一样充满了他的胸腔。他的气管通过嘴和鼻子向这里源源不断地提供空气。每次吸进来的空气,最终都会被送到小小的肺泡中。肺泡被很多纤细的血管包裹着。于是,在这些位于肺都最深处的肺泡中,血液里有害的二氧化碳与维系生命的氧气进行了交换。斯蒂文通过呼吸过 We cling to a carbon dioxide molecule and follow the foamy blood and go straight to a wide tube after we have taken a look at Steven’s heart and other body parts. Further forward, the tube is split into two; then, each branch continues to divide the narrower branch until the branch is narrow enough that we can not squeeze it over. Here, the whistling currents make a deafening noise - we’ve entered Steven’s lungs. This organ fills his chest like two sponge bags. His trachea supplies air continuously through the mouth and nose to here. Each time the air drawn in, will eventually be sent to a small alveoli. Alveoli are surrounded by many slender blood vessels. Thus, in these alveoli located in the deepest part of the lungs, the harmful carbon dioxide in the blood exchanges with the living oxygen. Steven breathe through