Intercostals

General information

The intercostal muscles are made up of the intrinsic muscles of the rib cage which are situated in the 11 intercostal spaces. There are three groups within the intercostals, situated superficially down to deep:

• External intercostal muscles
• Internal intercostal muscles
• Innermost intercostal muscles

Literal meaning

External intercostal muscles - the outward muscle between the ribs.

Internal intercostal muscles - the within (middle) muscle between the ribs.

Innermost intercostal muscles - the inmost muscle between the ribs.

Interesting information

These muscles are accessory respiratory muscles that aid in forced breathing. The external intercostals assist in forced inspiration, and the internal and innermost intercostals help with forced expiration.

Any deficits in the intercostal muscles may lead to chest wall movement during changes in thoracic pressure, this is because there is inadequate tension of the intercostal spaces. This can then cause respiratory insufficiency.

Origin

External, internal, and innermost intercostal muscles - Inferior border of superior rib.

Insertion

External, internal, and innermost intercostal muscles - Superior border of adjacent inferior rib.

Function

Mechanical support to the thoracic cage, accessory respiratory muscles.

Nerve supply

External, internal, and innermost intercostal muscles - Intercostal nerves (T1 through T11).

Blood supply

External intercostal muscles - anterior and posterior intercostal arteries.

Internal intercostal muscles - the anterior and posterior intercostal arteries, as well as from the costocervical trunk, internal thoracic and musculophrenic arteries.

Innermost intercostal muscles - the anterior and posterior intercostal arteries, costocervical trunk, internal thoracic and musculophrenic arteries.

Relevant research

None

Intercostal exercises

None