alveolus gas exchange

air alveoli alveolus anatomy artery biology blood body breath breathe breathing bronchi capillaries capillary carbon care cell chronic cross cutaway diagram dioxide disease education exchange exhale function gas gases great haemoglobin health healthcare healthy hemoglobin human illustration immune inhale labeled lung lungs medical medicine movement organ oxygen pulmonary red research respiration respiratory science section sections septal squamous structure surfactant system thin vector vessels water