The rib cage is flexible primarily to allow for breathing and movement.
The flexibility stems from a few key factors:
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Cartilage Connections: The ribs are connected to the sternum (breastbone) by costal cartilage. This cartilage is flexible, allowing the rib cage to expand and contract during respiration. Without this cartilage, breathing would be very difficult.
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Joints with Vertebrae: The ribs attach to the vertebrae (bones of the spine) in the back. These connections are not rigid; they include small joints that permit a gliding motion. This gliding allows the ribs to move slightly during breathing and other activities, contributing to the overall flexibility of the rib cage.
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Intercostal Muscles: Muscles between the ribs, called intercostal muscles, also play a role. These muscles contract and relax to help expand and contract the rib cage during breathing. They require a degree of flexibility in the rib cage to function effectively.
In summary, the flexible nature of the rib cage is essential for the mechanics of breathing and enables torso movements. The cartilage connections, the joints with the vertebrae, and the intercostal muscles all contribute to its necessary flexibility.