part of part of located_in respiratory tube bronchus BTO:0001340 CALOHA:TS-1229 EFO:0000932 EMAPA:32689 EV:0100041 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] FMA:7409 GAID:346 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 MA:0000436 MAT:0000133 MESH:D001980 MIAA:0000133 UBERON:0002185 UMLS:C0006255 VHOG:0000262 XAO:0000121 bronchi bronchial bronchial tissue bronchial trunk the upper conducting airways of the lung; these airways arise from the terminus of the trachea uberon thoracic cavity tracheobronchial tree