How does the diaphragm function in breathing?
The diaphragm provides main force for breathing.(other muscles are used during exercise, like the scalenes and the intercostals) When the diaphragm contracts it moves down into the abdomen by doing so it increases the volume of the thoracic cavity which in turn creates a negative pressure(compared to atmospheric) on the lungs(it actually creates a negative pressure in the intraplueral space). This negative pressure creates a pressure differential between the lungs and the atmosphere causing air to come into the lungs. During exhalation the diaphragm relaxes and the elastic force of the lung causes the air to be pushed outwards.
