The respiratory system meets this need by bringing oxygen to the bloodstream, which delivers it to each cell and carries away carbon dioxide. The lungs are the focal point of the respiratory system, which also includes the respiratory tract, the channel by which air flows into and out of the lungs. The drawing above is an illustration of the respiratory system. Inhaled air passes through the nose, where moisture and tiny hairs filter dust. It then passes down the throat where air is also humidified.
Air continues into the trachea.
Just above the heart, the trachea divides into two bronchi . The tiniest tubes end in globular air sacs called alveoli . There, blood vessels only one cell thick allow oxygen and carbon dioxide to trade places. The carbon dioxide is exhaled back up the respiratory tract. The blood picks up fresh oxygen and transports it throughout the body.