Muscle
Serratus anterior
Keeps the shoulder blade against the rib cage
High-yield
The long thoracic nerve supplies serratus anterior. Weakness can let the medial scapular border lift away from the chest wall.
Overview
Serratus anterior wraps from the upper lateral ribs to the rib-facing medial edge of the scapula. It carries the blade forward and, with trapezius, turns it upward to support reaching overhead.
Reference facts
- Origin
- Outer surfaces of the upper eight or nine ribs
- Insertion
- Costal surface along the medial scapular border, including its superior and inferior angles
- Action
- Protracts and upwardly rotates the scapula while holding it against the thoracic wall
- Innervation
- Long thoracic nerve, usually C5–C7
- Blood supply
- Lateral thoracic, superior thoracic and thoracodorsal arterial branches
Clinical correlation
Long thoracic nerve injury can produce medial winging and make overhead elevation weak or limited. The amount of remaining movement varies; it is not always blocked at exactly shoulder height.
Frequently asked questions
What does the serratus anterior do?
The serratus anterior protracts and upwardly rotates the scapula while holding it against the thoracic wall.
What nerve innervates the serratus anterior?
The serratus anterior is innervated by the long thoracic nerve, usually C5–C7.
Where does the serratus anterior attach?
The serratus anterior originates from the outer surfaces of the upper eight or nine ribs and inserts on the costal surface along the medial scapular border, including its superior and inferior angles.
What is the blood supply of the serratus anterior?
Lateral thoracic, superior thoracic and thoracodorsal arterial branches.