Thursday, April 12, 2012

The bronchi are the air passages into which the trachea divides, connecting it to the lungs. There are three kinds of bronchi: the primary bronchi, which are the main two branches (right and left) into which the trachea divides; the lobar bronchi, which are the secondary air passages given off by the primary bronchi; the tertiary bronchi are the smallest of the bronchial branches leading up to the bronchiole. Bronchi is plural of bronchus; so one branch is a bronchus, more than one are bronchi. Each bronchus is composed of three layers: the outermost is made up of dense fibrous tissue, reinforced with cartilage; the middle layer is a network of smooth muscle; and the innermost layer consists of ciliated mucous membrane.