Muscle
Subcostal muscles
Variable deep slips that bridge several ribs
High-yield
Identify these muscles by their posterior position and longer span. Their direction resembles the internal intercostals, and they belong to the deepest muscular layer.
Overview
Subcostal slips cross the inner posterior chest wall, usually most clearly in its lower part. Unlike a single-space intercostal muscle, a slip commonly reaches the second or third rib away. Their number and extent vary.
Reference facts
- Origin
- Inner rib surfaces around the posterior angles
- Insertion
- Usually the inner surface of a rib two or three levels below the upper attachment
- Innervation
- Nearby intercostal nerve branches
- Action
- Assist rib depression and support the posterior chest wall
- Blood supply
- Posterior intercostal arterial branches
Clinical correlation
The pattern is not uniform between people. Recognizing variable slips helps distinguish normal muscle from an unexpected structure when examining the inner thoracic wall.
Frequently asked questions
What do the subcostal muscles do?
Assist rib depression and support the posterior chest wall.
What nerve innervates the subcostal muscles?
The subcostal muscles are innervated by the nearby intercostal nerve branches.
Where do the subcostal muscles attach?
Origin: Inner rib surfaces around the posterior angles. Insertion: Usually the inner surface of a rib two or three levels below the upper attachment.
What is the blood supply of the subcostal muscles?
Posterior intercostal arterial branches.