Scalenus Anterior
Neck · Head & Neck
The scalenus anterior is the most anterior of the three scalene muscles of the lateral neck, an important surgical landmark because of the vital structures that pass around it. It arises from the transverse processes of the C3 to C6 vertebrae and descends to insert on the scalene tubercle of the first rib. Acting from above, it elevates the first rib to assist inspiration, and acting from below it flexes and laterally flexes the neck. It is supplied by the anterior rami of the cervical nerves (C4 to C6). The subclavian vein crosses in front of the muscle while the subclavian artery and brachial plexus pass behind it, making its relations clinically significant.
Origin, Insertion, Action & Nerve
Origin
Transverse processes of C3–C6
Insertion
Scalene tubercle of 1st rib
Action
Elevates 1st rib in inspiration; flexes and laterally flexes neck
Nerve
Anterior rami of cervical nerves (C4–C6)
Attachments explained
The Scalenus 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
Transverse processes of C3–C6
Insertion
Scalene tubercle of 1st rib
Action & function
When the Scalenus Anterior contracts, it produces the following movements: Elevates 1st rib in inspiration; flexes and laterally flexes neck.
As part of the Neck group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Scalenus Anterior receives its nerve supply from the Anterior rami of cervical nerves (C4–C6). This nerve carries fibres from spinal segment(s) C4, C6.
Because a muscle can only contract when its nerve is intact, injury to the Anterior rami of cervical nerves or to its spinal roots (C4, C6) can weaken or paralyse the Scalenus Anterior, impairing the movements it normally produces (elevates 1st rib in inspiration). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Scalenus Anterior (the OIANS method)
Study the scalenus anterior by its critical relations rather than in isolation, because the muscle is chiefly memorable for what runs past it. Fix that the subclavian vein passes anterior to it while the subclavian artery and the brachial plexus emerge behind it; this arrangement is the anatomical basis of thoracic outlet syndrome and separates the anterior scalene from its siblings.
For the action, reason from the attachments: running from the mid-cervical transverse processes down to the first rib, it can either hoist the rib for inspiration or bend the neck when the rib is fixed. Group it with scalenus medius and posterior as accessory muscles of respiration supplied by anterior cervical rami, then distinguish it by its first-rib scalene tubercle insertion.
Frequently asked questions
Where is the Scalenus Anterior located?
The Scalenus Anterior is a muscle of the Neck group, located in the Head & Neck.
What is the origin of the Scalenus Anterior?
Transverse processes of C3–C6
What is the insertion of the Scalenus Anterior?
Scalene tubercle of 1st rib
What movements does the Scalenus Anterior produce?
Elevates 1st rib in inspiration; flexes and laterally flexes neck
What nerve supplies the Scalenus Anterior?
Anterior rami of cervical nerves (C4–C6)
Is the Scalenus Anterior free to study in OIANS?
The Scalenus Anterior is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Head & Neck is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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