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- The internal intercostals attach from rib #1 to rib #12.
- Depress ribs #1-11 at the sternocostal and costospinal joints.
- Elevate ribs #2-12 at the sternocostal and costospinal joints.
- Ipsilaterally rotate and flex the trunk at the spinal joints (anterior fibers).
- Laterally flex the trunk at the spinal joints (lateral fibers).
- Extend the trunk at the spinal joints (posterior fibers).
- The internal intercostals are located within the intercostal spaces.
- Generally, muscles that elevate ribs act to create inspiration; generally muscles that depress ribs act to create expiration.
- There is controversy regarding the inspiration/expiration role of the internal intercostals.
- Directly superficial to the internal intercostals are the external intercostals.