Question

how does airflow in the lung depend on differences
in pressure??

Answer 1

Inspiration(diaphragm moves down ,accessory muscles move out)---->negative intra-thoracic pressure--->air moves in

Expiration(diaphragm moves up to normal position, accessory muscles of respiration relaxes, bringing back the chest wall to relaxed position)----->Intra-thoracic pressure returns to normal--->air moves out

Answer 2

http://biology.slss.ie/resources/respiratory%20system.ppt

Answer 3

when a gas is under pressure, it's going to try and move into a place where the pressure is less. pressure is inversely proportional to volume, which means that if the volume/space increases, then the pressure inside said space is going to decrease, thus the gas will want to move in that direction. when you inhale, your inspiratory muscles (diaphragm, external intercostal muscles) create a greater volume in the thorasic cavity, and thus decreasing the pressure in your chest. because of this decrease in pressure, air is going to flow in towards the cavity until the pressure in your chest is slightly higher than that of external air. when you get to that point, the inspiratory muscles relax (if breathing at a faster and harder rate, expiratory muscles may come into play: abdominal and internal intercostal muscles) and air flows back out towards the smaller pressure.