respiratory tube bronchiole https://upload.wikimedia.org/wikipedia/commons/d/db/Alveoli_diagram.png lacks submucosa and cartilage plates; they have 3 layers: mucosa, muscular layer and outer layer EHDAA:8183 EMAPA:32697 The conducting airway of the lungs found terminal to the bronchi; these structures contain neither cartilage nor mucous-secreting glands; the epithelium of the bronchioles becomes thinner with each branching. UMLS:C0006270 In some texts/references/ontologies, bronchiole has been used as an exact synonym of 'lobular bronchiole'. However, a 'lobular bronchiole' is a segment of a bronchiole. bronchiolus VHOG:0000675 EHDAA:8221 EHDAA:8171 Wikipedia:Bronchiole MESH:D055745 UBERON:0002186 CALOHA:TS-2003 MA:0000422 bronchioli uberon FMA:7410 In FMA2 and FMA3, lobular bronchiole is an exact synonym of bronchiole; however, there are two distinct terms for the corresponding epithelium. bronchiolar EHDAA:8199 NCIT:C12684 SCTID:278982001 BTO:0002375