bronchial tree, an anatomical complex of the trachea and bronchi. The bronchi branch from the trachea. The right bronchus is wider and shorter than the left bronchus and branches into three secondary bronchi, one passing to each of the three lobes of the right lung. The left bronchus is smaller in diameter and about twice as long as the right bronchus. It is also more horizontal and more susceptible to obstruction. It branches into the secondary bronchi for the inferior and the superior lobes of the left lung. The bronchus is sometimes described as a bronchial tube.