The Chest Muscles
thoracic
Where the chest muscle connect
Effective Methods of Breathing
Collarbones
Clavicular Breathing
Air Supply
Intercostals
- Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
- Actions: The interosseous part reduces the thoracic volume by depressing the rib cage, and the interchondral part elevates the ribs.
- Innervation: Intercostal nerves (T1-T11).
External Intercostals
There are 11 pairs of external intercostal muscles. They run inferoanteriorly from the rib above to the rib below, and are continuous with the external oblique of the abdomen.
- Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
- Actions: Elevates the ribs, increasing the thoracic volume.
- Innervation: Intercostal nerves (T1-T11).
Innermost Intercostals
These muscles are the deepest of the intercostal muscles, and are similar in structure to the internal intercostals.
They are separated from the internal intercostals by the intercostal neurovascular bundle and are found in the most lateral portion of the intercostal spaces.
- Attachments: Originate at the lower border of the rib, inserting into the superior border of the rib below.
- Actions: The interosseous part reduces the thoracic volume by depressing the rib cage, and the interchondral part elevates the ribs.
- Innervation: Intercostal nerves (T1-T11)
Transversus Thoracis
These muscles of the thoracic cage are continuous with transversus abdominis inferiorly.
- Attachments: From the posterior surface of the inferior sternum to the internal surface of coastal cartilages 2-6.
- Actions: Weakly depress the ribs.
- Innervation: Intercostal nerves (T1-T11).
Subcostals
The subcostal muscles are found in the inferior portion of the thoracic wall. They comprise of thin slips of muscle, which run from the internal surface of one rib, to second and third ribs below. The direction of the fibres parallels that of the innermost intercostal.
- Attachments: These originate from the inferior surface of the lower ribs, near the angle of the rib. They then attach to the superior border of the rib 2 or 3 below.
- Actions: Share the action of the internal intercostals
- Innervation: Intercostal nerves