In the mouse, nerves were located throughout the trachea and extrapulmonary bronchi in both the smooth muscle and the connective tissue. However, no nerves were found within the epithelium. In the smooth muscle there were large numbers of nonmyelinated nerves. These were usually ‘en passant’ elements but varicosities containing small mitochondria and vesicles were also seen; these axons sometimes appeared to be efferent to the mus
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