respiratory tube bronchus http://upload.wikimedia.org/wikipedia/commons/1/18/Respiratory_system_complete_numbered.svg UMLS:C0006255 UBERON:0002185 MESH:D001980 FMA:7409 MAT:0000133 uberon EV:0100041 MIAA:0000133 GAID:346 EMAPA:32689 EFO:0000932 NCIT:C12683 BTO:0001340 bronchi VHOG:0000262 XAO:0000121 The upper conducting airways of the lung; these airways arise from the terminus of the trachea. bronchial trunk MA:0000436 bronchial In humans, the main bronchus is histologically identical to trachea; 2ary and 3ary bronchi are not; epithelium becomes simple columnar, goblet cell number decreases, elastic fibers in lamina propria increases, distribution more uniform. Muscular layer between mucosa and submucosa appears. cartilage rings become discontinuous plates connected by fibrous connective tissue CALOHA:TS-1229 bronchial tissue Each of the two primary divisions of the trachea leading respectively into the right and the left lung. [Dorian_AF, Elsevier's_encyclopaedic_dictionary_of_medicine, Part_B:_Anatomy_(1988)_Amsterdam_etc.:_Elsevier][VHOG]