Internal intercostals

Internal intercostals

Anatomy

Origin:
Lateral edge of costal groove of the rib above.

Insertion:
Superior surface of the rib below.

Key relations:
-Muscle fibres run in the opposite direction to the external intercostals i.e. run obliquely posteroinferiorly.
-Insert deep to the insertion of the external intercostals.

Functions

-Moves ribs inferiorly during expiration, thereby contracting the thoracic cavity.
-Maintains intercostals spaces during inspiration and expiration.

Supply

Nerve Supply:
Intercostal nerves T1 to T11.

Blood Supply:
Intercostal arteries.

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