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 OpenCyc:Mx4rvl9iDpwpEbGdrcN5Y29ycA 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 bronchiolus VHOG:0000675 EHDAA:8221 EHDAA:8171 UBERON:0002186 CALOHA:TS-2003 lobular bronchiole MA:0000422 bronchioli uberon FMA:7410 bronchiolar EHDAA:8199 NCIT:C12684 BTO:0002375