Because if it all stays in then your body will keep in this poisons gases. http://wiki.answers.com/Why_does_air_move_in_our_out_of_your_respiratory_system#ixzz1ZCdvdlbk
the lungs and respiratory system
diffusion
Material moves from the respiratory system to the circulatory system by diffusing across a membrane in the air sacks called alveoli.
Because if it all stays in then your body will keep in this posions gass.
Air sacs are part of the respiratory system
Respiratory System
the respiratory system
Cilia are the tiny hairs that sweep dust and dirt out of the respiratory system.
The respiratory system is the organ system that moves air into and out of your body.
Material moves from the respiratory system to the circulatory system by diffusing across a membrane in the air sacks called alveoli.
Air can be taken into the respiratory system at the mouth and the nose.
Mucus in the nose helps trap particles entering the respiratory system. The hairs/cilia of the respiratory system also filter incoming air.