part_of part of part of Homo sapiens lung alveolar sac alveolus of lung https://upload.wikimedia.org/wikipedia/commons/4/46/Alveolus_diagram.svg CALOHA:TS-0031 UBERON:0002299 respiratory alveolus SCTID:361364000 BTO:0000060 alveolus pulmonis alveoli GAID:349 alveolus FMA:7318 Spherical outcropping of the respiratory bronchioles and primary site of gas exchange with the blood. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates[WP]. EFO:0001985 lung alveolus EMAPA:32682 MA:0000420 VHOG:0001445 alveolus pulmonis respiratory alveoli Wikipedia:Pulmonary_alveolus MESH:D011650 pulmonary alveolus alveolus lung structure