Ventilation of the lungs is the first step in the supply of oxygen to the tissues and the last step in the excretion of carbon dioxide .
(Ventilation of the lungs; is; the first step in the supply of oxygen to the tissues and the last step in the excretion of carbon dioxide)
Ventilation of the lungs
is
the first step in the supply of oxygen to the tissues and the last step in the excretion of carbon dioxide