Serratus Anterior
Shoulder & Scapula · Upper Limb
The serratus anterior is a broad, fan-shaped muscle covering the lateral rib cage, its fleshy digitations giving a saw-toothed appearance. It arises from the external surfaces of ribs 1 to 8 and wraps around the thorax to insert on the anterior (costal) surface of the medial border of the scapula. It protracts the scapula (as in a boxer's punch), upwardly rotates it to allow the arm to be raised overhead, and, crucially, holds the scapula flat against the thoracic wall. It is supplied by the long thoracic nerve (C5, C6, C7); injury to this nerve causes a winged scapula and an inability to raise the arm above the horizontal.
Origin, Insertion, Action & Nerve
Origin
External surfaces of ribs 1–8 (fleshy digitations)
Insertion
Anterior (costal) surface of medial border of scapula
Action
Protracts and upwardly rotates scapula; holds scapula against thoracic wall
Nerve
Long thoracic nerve (C5, C6, C7)
Attachments explained
The Serratus Anterior is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
External surfaces of ribs 1–8 (fleshy digitations)
Insertion
Anterior (costal) surface of medial border of scapula
Action & function
When the Serratus Anterior contracts, it produces the following movements: Protracts and upwardly rotates scapula; holds scapula against thoracic wall.
As part of the Shoulder & Scapula group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Serratus Anterior receives its nerve supply from the Long thoracic nerve (C5, C6, C7). This nerve carries fibres from spinal segment(s) C5, C6, C7.
Because a muscle can only contract when its nerve is intact, injury to the Long thoracic nerve or to its spinal roots (C5, C6, C7) can weaken or paralyse the Serratus Anterior, impairing the movements it normally produces (protracts and upwardly rotates scapula). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Serratus Anterior (the OIANS method)
Understand serratus anterior through its two jobs: it protracts the scapula (the punching motion) and it upwardly rotates it so the arm can go overhead. Because it wraps from the ribs around to the front of the medial border of the scapula, its pull naturally slides the shoulder blade forward and swings the glenoid upward. The boxer's punch image ties action to attachment instantly.
The unforgettable hook is the winged scapula. Learn the mnemonic that the long thoracic nerve is derived from C5, C6, C7 and keeps the wings on the ground: lose it and the medial border of the scapula lifts off the back, and the arm cannot be raised above horizontal. Reasoning from that deficit back to the muscle's normal action cements everything.
Frequently asked questions
Where is the Serratus Anterior located?
The Serratus Anterior is a muscle of the Shoulder & Scapula group, located in the Upper Limb.
What is the origin of the Serratus Anterior?
External surfaces of ribs 1–8 (fleshy digitations)
What is the insertion of the Serratus Anterior?
Anterior (costal) surface of medial border of scapula
What movements does the Serratus Anterior produce?
Protracts and upwardly rotates scapula; holds scapula against thoracic wall
What nerve supplies the Serratus Anterior?
Long thoracic nerve (C5, C6, C7)
Is the Serratus Anterior free to study in OIANS?
Yes. The Serratus Anterior is free in OIANS: its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory, and because it belongs to the Upper Limb it is also covered by the free Quiz and Flashcard decks. The other regions, the "All Muscles" deck, and the Progress and Explore tools are unlocked with a one-time Lifetime purchase.
Related muscles
Study the Serratus Anterior
Test yourself on Upper Limb muscles with interactive quizzes and flashcards in the free OIANS app.
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