The interior of lung is divided into millions of small chambers called "P". The "P" increasing the moist surface available for transfer of gases between air and "Q". The lining of the lung are much folded and so their total surface is enormous. If all "P" of our lungs are spread out they will cover an area of nearly 160 m sq. The "Q" supplies Oxygen to the tissue to carry out "R".
What is the process "R"???
Which system is described in the above comprehension???
What happens if there are no folds at the lining of lungs???