人体的呼吸道从鼻腔开始,经咽喉、声门、气管、支气管,最后到达肺泡。以声门为界,声门以上称上呼吸道,声门以下称下呼吸道。呼吸道在人体各器官中与外界环境接触最为频繁,接触面积最大。人体皮肤的表面积一般不超过2平方米,而成人肺泡多达3～7.5亿个,总面积可达100平方米。一个 The human respiratory tract from the nasal cavity, the throat, glottis, trachea, bronchi, and finally reach the alveoli. To the glottis as the boundary, above the glottis said upper respiratory tract, glottis below the lower respiratory tract. Respiratory tract in the human body organs and the external environment in the most frequent contact with the largest contact area. Human skin surface area generally not more than 2 square meters, while adult alveoli up to 3 to 750 million, with a total area of ​​up to 100 square meters. One