Now, these structures are basically the ribs and this is our ribcage. Now, in between the ribs, we have these red portions, and that is the external intercostal muscle, a type of skeletal muscle. And beneath the lungs, we have another type of skeletal muscle we call the diaphragm. The diaphragm is basically a dome shaped skeletal muscle that is found below the lungs and which separates the thoracic cavity, the chest cavity, where the lungs are found, and our abdominal cavity, which is found beneath our diaphragm. So let's describe how inhalation actually takes place. So the diaphragm, as well as these external intercostal muscles found between our ribs, begin to actually use ATP and contract.