The Airways and the Lungs

Five parts on getting air to the blood. It opens on the conducting zone — the branching pipework from nose to the smallest tubes, which carries air without exchanging any of it, and warms and cleans it on the way. Two parts then take the larynx from the front and cut open, an organ doing two jobs at once: guarding the entrance to the airway, and making the sound of your voice from a pair of folds under tension. The fourth part is the lungs themselves, lobed differently on the two sides because the heart takes up room on the left. The last follows blood through them, which is the only circuit in the body where the artery carries the deoxygenated blood.