Muscle
External intercostals
Outer intercostal layer that helps lift the ribs
High-yield
The external layer assists rib elevation and supports the spaces between ribs during breathing. Its fiber direction differs from that of the internal layer.
Overview
These muscles link neighboring ribs in eleven spaces on each side. Viewed along the side of the chest, their fibers slope downward and forward. Near the costal cartilages, an external intercostal membrane continues the layer.
Reference facts
- Origin
- Lower edge of the rib above each space
- Insertion
- Upper edge of the next rib down
- Action
- Assists inspiration by elevating ribs and stabilizing the intercostal spaces
- Innervation
- Intercostal nerves from thoracic anterior rami, T1–T11
- Blood supply
- Anterior and posterior intercostal arterial branches
Frequently asked questions
What do the external intercostals do?
Assists inspiration by elevating ribs and stabilizing the intercostal spaces.
What nerve innervates the external intercostals?
The external intercostals are innervated by the intercostal nerves from thoracic anterior rami, T1–T11.
Where do the external intercostals attach?
The external intercostals originate from the lower edge of the rib above each space and insert on the upper edge of the next rib down.
What is the blood supply of the external intercostals?
Anterior and posterior intercostal arterial branches.