Ventrolateral view, left side

The diaphragm is primarily skeletal muscle.  Functionally it is very important because it is responsible for most breathing at rest.  It is dome shaped.  In humans the origin of the diaphragm is along its outer margin to the deep surface of the bony thorax, costal cartilage of the ribs 7 to 12, sternum, and lumbar vertebrae 1 through 3.  The insertion is at the central tendon.  The phrenic nerve serves the diaphragm.