Explain the process by which inhalation occurs during breathing in human beings.

(N/A) $1$. Inhalation is the process of taking oxygen-rich air into the lungs.
$2$. During this process, the diaphragm, which is a dome-shaped muscular sheet separating the chest cavity from the abdominal cavity, contracts and moves downward.
$3$. Simultaneously, the rib muscles contract, lifting the ribs and expanding the chest cavity.
$4$. This increase in the volume of the chest cavity leads to a decrease in air pressure inside the lungs compared to the atmospheric pressure.
$5$. Consequently, air from the outside rushes into the lungs through the nostrils to equalize the pressure.