Far below sea level, they contain some of the harshest environments on Earth, with no oxygen and no light.

VOA: special.2010.11.10

The respiratory system plays an important role in maintaining our internal environment at the proper level of oxygen, by bringing the right amount in.

呼吸系统的重要性在于,通过向体内输入适量的氧气,维持人体内环境中的氧平衡

耶鲁公开课 - 生物医学工程探索课程节选