It's a muscle in your chest that expands your chest size when you breath in and decreases size when you breathe out. (i think you might want to double check.).
Hope this helps!
diaphagram is that major muscle
The diaphragm on a microscope is a circular disk placed beneath the stage that controls the amount of light entering the specimen. By adjusting the diaphragm, you can improve the contrast and clarity of the image by regulating the amount of illumination.
the big toe on right foot to stimulate right cerebral hemisphere solar plexus to relax and destres lungs and diaphagram to increase o2 and cos