RT Book, Section A1 Ciccone, Charles D. SR Print(0) ID 1135036719 T1 Respiratory Drugs T2 Pharmacology in Rehabilitation YR 2016 FD 2016 PB F. A. Davis Company PP New York, NY SN 9780803640290 LK fadavispt.mhmedical.com/content.aspx?aid=1135036719 RD 2024/03/18 AB The respiratory system is responsible for mediating gas exchange between the external environment and the bloodstream. The upper respiratory tract conducts air to the lower respiratory passages and ultimately to the lungs. It also humidifies and conditions inspired air and serves to protect the lungs from harmful substances. In the lungs, gas exchange takes place between the alveoli and the pulmonary circulation.