Internal Intercostals

Joe Muscolino

Share This

Anterior and posterior views of the internal intercostal muscles.
ATTACHMENTS:

  • The internal intercostals attach from rib #1 to rib #12.

 

ACTIONS:

  • 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).

 

NOTES:

  1. The internal intercostals are located within the intercostal spaces.
  2. Generally, muscles that elevate ribs act to create inspiration; generally muscles that depress ribs act to create expiration.
  3. There is controversy regarding the inspiration/expiration role of the internal intercostals.
  4. Directly superficial to the internal intercostals are the external intercostals.