alveolus gas exchange

gas exchange alveolar bronchiole sac pulmonary alveolus capillary red blood cell closeup respiratory system alveoli oxygen lung hemoglobin human anatomy respiration air bronchi lungs capillaries medical organ health science biology structure medicine carbon dioxide disease education breathe healthy artery haemoglobin healthcare care chronic cross cutaway diagram immune labeled research sections vector function ii septal great vessels thin movement squamous water surfactant gases poster isometric flat