Name the important parts involved in creating a pressure gradient between the lungs and the atmosphere during normal respiration.

(N/A) During normal respiration,the creation of a pressure gradient between the lungs and the atmosphere is primarily facilitated by the diaphragm and the external intercostal muscles.
$1$. The diaphragm contracts and flattens,increasing the volume of the thoracic cavity in the anteroposterior axis.
$2$. The external intercostal muscles contract,lifting the ribs and the sternum,which increases the volume of the thoracic cavity in the dorsoventral axis.
$3$. These combined actions increase the overall thoracic volume,which leads to a decrease in intrapulmonary pressure below atmospheric pressure,allowing air to flow into the lungs.