Now, because the diaphragm is a skeletal muscle, that means we have voluntary control of our diaphragm. It is controlled by the somatic nervous system. Now, our lungs are not actually by themselves, they are encased in this membrane we call the cirrus membrane and we call it a sears membrane because as we'll see in just a moment, it actually contains a fluid. Now, this sears membrane consists of two individual membranes. We have an outer membrane and we have an inner membrane. So this is a two layer protective barrier that encloses our lungs.