Function of the Respiratory System. The function of the human respiratory system is to transport air into the lungs and to facilitate the diffusion of Oxygen into the blood stream.Its also receives waste Carbon Dioxide from the blood and exhales it.arts of the Upper Respiratory Tract. 1  Mouth, nose & nasal cavity: The function of this part of the system is to warm, filter and moisten the incoming air. 2  Pharynx: Here the throat divides into the trachea (wind pipe) and oesophagus (food pipe). 3  Larynx: This is also known as the voice box as it is where sound is generated.