Aging and the Pulmonary System
Your pulmonary system, i.e. your lungs and airways, is located in your chest and surrounded by muscles, which are necessary for your breathing, and by bones, which protect your lungs and provide a scaffold to which your mucles are attached. Your lungs are protected by the immune system from infection. Agings affects all these components of your body.
A major component of your lungs are alveoli (see the picture), and they lose thier shape with age. This in turns lead to worsening air exchange between your lungs and blood. In addition, air may get trapped there.
Your muscles and bones weaken with age, which leads to an imperfect air exchange between lungs and the outside air. This leads again to less oxygen in your blood, and increase levels of carbon dioxide, which would have been otherwise breathed out.
Finally, you immune system weakens with age, and is no longer able to fight dieases as efficiently as in your youth. This results in increased infections, which again weaken the lung. Smoking does not help and further damages your lung.