Trachea and lung bronchi. Historical anatomical artwork of the human trachea and lung bronchi, seen from the front. The trachea (windpipe, upper centre), brings air from the mouth down the throat and into the lungs. The trachea splits (centre) into two bronchi, one for each lung. The bronchi subdivide into bronchioles (smaller airways) that themselves branch into smaller airways, eventually ending in alveolar sacs where oxygen is passed into the bloodstream. Artwork from the 19th- century book Atlas of Anatomy, by Bourgery and Jacob. This book, which took over 20 years to complete, was published in France in 8 volumes from 1831 to 1854. It contained 726 colour plates covering both anatomy and surgical techniques.