what structures exist in the lower respiratory system
Drawing In and Processing Air: How the Structures of the Lower Respiratory System Work The lower respiratory system, or lower respiratory tract, consists of the trachea, the bronchi and bronchioles, and the alveoli, which make up the lungs.t extends from the bottom of the larynx down behind the sternum, until it branches into smaller tubes, the bronchi. During inhalation, air filtered and warmed by the upper respiratory system passes from the pharynx and larynx into the trachea, then down to the bronchi and into the lungs.