DAVID GIFFORD / SCIENCE PHOTO LIBRARY DAVID GIFFORD / SCIENCE PHOTO LIBRARY
Respiratory system. Illustration showing the human respiratory system on a female figure. The trachea (windpipe) contains rings of supporting cartilage. The trachea takes air from the mouth and nose to the two lungs (pink, in the chest). The trachea branches into a bronchus for each lung, and each bronchus splits further into bronchioles. Further branching finally ends in alveoli (too small to be seen). These are air sacs where gas exchange takes place with the blood. Oxygen in the air is taken up by the blood for transport to body tissues. The waste gas carbon dioxide (produced by metabolic processes in the body) is released by the blood into the lungs and exhaled.
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