<P> In multicellular organisms therefore , specialised respiratory organs such as gills or lungs are often used to provide the additional surface area for the required rate of gas exchange with the external environment . However the distances between the gas exchanger and the deeper tissues are often too great for diffusion to meet gaseous requirements of these tissues . The gas exchangers are therefore frequently coupled to gas - distributing circulatory systems , which transport the gases evenly to all the body tissues regardless of their distance from the gas exchanger . </P>
<P> In multicellular organisms therefore , specialised respiratory organs such as gills or lungs are often used to provide the additional surface area for the required rate of gas exchange with the external environment . However the distances between the gas exchanger and the deeper tissues are often too great for diffusion to meet gaseous requirements of these tissues . The gas exchangers are therefore frequently coupled to gas - distributing circulatory systems , which transport the gases evenly to all the body tissues regardless of their distance from the gas exchanger . </P>
which body structure provides actual diffusion of respiratory gases in lungs
which body structure provides actual diffusion of respiratory gases in lungs
circulatory systems
circulatory systems