Gas exchange in the alveolus
A    Alveoli
B    Section of alveolus
C    Blood flow
D    Inhaled air (rich in oxygen)
E    Exhaled air(poor in oxygen)
F    Diffusion of oxygen in blood
G    Diffusion of carbon dioxide from blood
1    Branch of pulmonary artery
2    Capillary network
3    Respiratory bronchiolo
4    Branch of pulmonary vein
5    Alveolus
6    Red blood cell
7    Capillary wall
8    Epithelium of alveolus
9    Film of moisture
10    Blood plasma