How do the ribs move during breathing?

The rib cage is a semirigid, expansile structure that facilitates breathing through specific mechanical movements at the joints between the ribs and the vertebral column. These joints permit a gliding motion that allows the rib cage to change size during the respiratory cycle.12

Inspiration

During inspiration, the external intercostal muscles contract, causing the ribs to rotate upward and laterally. This movement increases the circumference of the chest cavity. By expanding the chest, the pressure within the lungs is reduced below atmospheric pressure, drawing air into the lungs to restore equilibrium.32

Expiration

Expiration is primarily a passive process resulting from the relaxation of respiratory muscles and the elastic recoil of the lungs and thoracic skeleton. However, during labored breathing or exercise, the internal intercostal muscles and abdominal muscles are activated to actively depress the rib cage and decrease the chest circumference, forcing air out of the lungs.234