The Physics of Gas Exchange Across the Avian Eggshell

The principles which govern gas exchange by diffusion across the pores of the avian eggshell are reviewed and compared with convective gas exchange. The concept of conductance is defined for both diffusive and convective gas exchange through pores, and methods of calculating pore size are described. Estimates of conductances of the elements in the gas transfer path from atmosphere to chorioallantoic capillary blood are discussed, and recent studies on the role of ternary diffusion and a convective component to gas fluxes are presented.