air moves into the lungs when atm. pressure is greater than pressure within lungs or atm. pressure less within lungs?
Air moves into the lungs when the atmospheric pressure is greater than the air pressure in lungs, as a result, air from atmosphere quickly rushes into lungs to equalise the air pressure on both sides. The negative pressure inside the lungs is created by increasing the volume of thoracic cavity. It is done by contracting the diaphragm and intercostal muscles.