inspiration

• external intercostal and diaphragm muscles contract
• causes the ribcage to move up and out, increasing the volume of the thorax and the diaphragm flattens
• as the volume of the thorax increases the lung pressure decreases and this causes air to flow into the lungs
• inspiration is an active process - needs energy
• diaphragm muscles contract, causes diaphragm to move down and flatten
• ribs move outwards and upwards