Describe the path of a molecule of oxygen from the nostril into the pulmonary capillaries of the lungs. Be sure to include ALL the structures through which the air passes in the correct sequence, until it reaches the capillaries of the lungs. Describe the path of a molecule of oxygen from the nostril into the pulmonary capillaries of the lungs. Be sure to include ALL the structures through which the air passes in the correct sequence, until it reaches the capillaries of the lungs..