This illustration shows the respiratory ducts with larynx, trachea and lungs. The larynx with the thyroid gland and its cricoid cartilage is depicted in the middle. It continues with the trachea that divides into left and right main bronchus. The main bronchi divide into two or three secondary bronchi, and the lobar bronchi divide into tertiary bronchi, which can be seen on the right side of the picture. On the left side: Lung divided into a superior, medial, and inferior lobe by the oblique and horizontal fissure.