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Why are costal cartilages important for movement of the ribs during breathing?

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Front and back views of the human skeleton are shown side by side, with labeled bones including the skull, spine, ribs, pelvis, arms, legs, hands, and feet. Insets detail the bones of the foot and hand, highlighting major bone groups and anatomical terms. — human skeleton Front and back views of the human skeleton.

The rib cage is a semirigid but expansile structure, and costal cartilages are essential to this functionality. These pliable cartilages attach the first seven pairs of ribs directly to the sternum, while the cartilages of the next three pairs connect to the cartilage above them.123

Because these attachments are pliable rather than rigid, they allow the rib cage to increase in size during inspiration. As respiratory muscles—such as the diaphragm and external intercostal muscles—contract, the ribs rotate and move, expanding the chest cavity. This expansion reduces the air pressure within the lungs, facilitating the intake of air. Without the flexibility provided by the costal cartilages, the rib cage would be too rigid to permit the necessary movement and expansion required for effective breathing.124