Because that is where the primary gas exchange happens.
The lungs are the main organ of the respiratory system, but they are also an organ in the circulatory system.
The respiratory system.
The lungs.
The respiratory system. The alveoli are air sacs in the lungs.
Respiratory.
The lungs.
The main organ in the respiratory system the lungs.
The lungs are part of the respiratory system (breathing)
the respiratory system
lungs
lungs
Heart: Circulatory system. Lungs: Respiratory system.