part of part of has part contributes to morphology of lung epithelium respiratory tube alveolar sac NCIT:C32057 The small terminal dilation of the alveolar ducts around which the alveoli form pocket-like clusters. sacculus alveolaris MA:0000418 Wikipedia:Alveolar_sac pulmonary alveolar sac BTO:0000061 SCTID:361964007 EMAPA:35119 UBERON:0002169 air sac FMA:7317 UMLS:C0225691 alveolus of lung alveolar system epithelial sac pulmonary acinus