What is Residual Volume and what is its importance?

Residual volume is the amount of gas remaining in the lungs at the end of a maximal exhalation.

Residual Volume is important because it prevents the lungs from collapsing.

Even after we have expelled as much air as possible (expiratory reserve volume) gaseous exchange is still occurring by residual volume in the lungs.

It also prevents the inner surfaces of the lungs sticking together.