ALFRED PASIEKA / SCIENCE PHOTO LIBRARY ALFRED PASIEKA / SCIENCE PHOTO LIBRARY
Lung airways. Computer-enhanced image of a resin cast of the airways in the lungs. The trachea (windpipe, top centre) divides into two main bronchi. These branch further into smaller bronchi and then bronchioles. The bronchioles terminate in alveoli (not seen), grape-like clusters of air sacs surrounded by blood vessels. Here, the blood takes up oxygen and releases carbon dioxide to be exhaled.
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