The muscles associated with the thoracic cage include those involved in respiration, stabilization of the ribcage, and movements of the shoulder and upper limb. Here is a list of some major muscles of the thoracic cage, along with their attachments, nerve supply, and actions:

1. External Intercostal Muscles:
   • Attachments:
     • Origin: Inferior border of a rib.
     • Insertion: Superior border of the rib below.
   • Nerve Supply: Intercostal nerves.
   • Actions: Elevate the ribs during inspiration, assisting in inhalation.
2. Internal Intercostal Muscles:
   • Attachments:
     • Origin: Superior border of a rib.
     • Insertion: Inferior border of the rib above.
   • Nerve Supply: Intercostal nerves.
   • Actions: Depress the ribs during expiration, assisting in exhalation.
3. Innermost Intercostal Muscles:
   • Attachments:
     • Similar to internal intercostals.
   • Nerve Supply: Intercostal nerves.
   • Actions: Assist in expiration by depressing the ribs.
4. Diaphragm:
   • Attachments:
     • Origin: Sternal (costal) part – xiphoid process and costal cartilages; Costal (lumbar) part – inner surface of lower six ribs and their costal cartilages; Lumbar (vertebral) part – two crura attaching to lumbar vertebrae.
     • Insertion: Central tendon.
   • Nerve Supply: Phrenic nerve (C3-C5).
   • Actions: Major muscle of inspiration; contracts to increase the thoracic volume during inhalation.
5. External Oblique:
   • Attachments:
     • Origin: External surfaces of lower eight ribs.
     • Insertion: Linea alba, pubic crest, and anterior iliac crest.
   • Nerve Supply: Intercostal nerves and subcostal nerve (T7-T12).
   • Actions: Flexes and rotates the trunk; compresses the abdomen.
6. Internal Oblique:
   • Attachments:
     • Origin: Inguinal ligament, iliac crest, and lumbodorsal fascia.
     • Insertion: Lower three ribs, linea alba, and pubic crest.
   • Nerve Supply: Intercostal nerves and subcostal nerve (T7-T12).
   • Actions: Flexes and rotates the trunk; compresses the abdomen.
7. Rectus Abdominis:
   • Attachments:
     • Origin: Pubic crest and symphysis.
     • Insertion: Xiphoid process and costal cartilages of ribs 5-7.
   • Nerve Supply: Intercostal nerves (T7-T12).
   • Actions: Flexes the trunk; compresses the abdomen.
8. Transversus Abdominis:
   • Attachments:
     • Origin: Inguinal ligament, iliac crest, and lumbodorsal fascia.
     • Insertion: Linea alba, pubic crest, and costal cartilages.
   • Nerve Supply: Intercostal nerves and subcostal nerve (T7-T12).
   • Actions: Compresses the abdomen.
9. Serratus Posterior Superior:
   • Attachments:
     • Origin: Spinous processes of C7-T3.
     • Insertion: Upper ribs (2-5).
   • Nerve Supply: Intercostal nerves.
   • Actions: Elevates the ribs during deep inspiration.
10. Serratus Posterior Inferior:
    • Attachments:
      • Origin: Spinous processes of T11-L2.
      • Insertion: Lower ribs (8-12).
    • Nerve Supply: Intercostal nerves.
    • Actions: Depresses the ribs during forced expiration.

It’s important to note that the actions mentioned are simplified, and many muscles contribute to a variety of movements. Additionally, individual anatomical variations may exist.

Video Lecture of above content

Download PowerPoint Slide for Lecture