lung alveoli supporting vital respiration and oxygen flow

lung alveoli supporting vital respiration oxygen flow lungs blood exchange carbon dioxide process breathing breathed air passes travels tissues body alveoli respiration respiratory anatomy lung bronchi medicine coronavirus oxygen pulmonary medical system organ diagram human health circulation structure breathing inhale trachea air capillaries exchange airway bronchial dioxide pneumonia vessels bronchiole gas exhale scientific scheme science cancer educational carbon detailed biology illness blood flow growth asthmatic covid-19 swollen