Explanation

Inspiration, or inhalation, involves the contraction of two main muscle groups:

Diaphragm: a dome-shaped muscle that separates the chest cavity from the abdominal cavity.

When it contracts, it flattens and increases the volume of the chest cavity.

Intercostal muscles: muscles located between the ribs.

When they contract, they pull the ribs outward and upward, increasing the volume of the chest cavity.