Scalenus Minimus
Neck · Head & Neck
The scalenus minimus is an inconstant deep muscle of the neck that, when present, lies at the root of the neck behind the anterior scalene. It typically arises from the anterior tubercle of the transverse process of C7 and descends to attach to the inner border of the first rib and the suprapleural membrane, also known as Sibson's fascia, which roofs over the cervical pleura. Its main described role is to tense this suprapleural membrane and thereby support the apex of the lung, and it may assist in elevating the first rib. It is supplied by the anterior ramus of C7, sometimes with a contribution from C8.
Origin, Insertion, Action & Nerve
Origin
Anterior tubercle of the transverse process of C7 (variable)
Insertion
Inner border of the first rib and the suprapleural membrane (Sibson's fascia)
Action
Tenses the suprapleural membrane; may elevate the first rib (inconstant variant)
Nerve
Anterior ramus of C7 (and C8)
Attachments explained
The Scalenus Minimus 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
Anterior tubercle of the transverse process of C7 (variable)
Insertion
Inner border of the first rib and the suprapleural membrane (Sibson's fascia)
Action & function
When the Scalenus Minimus contracts, it produces the following movements: Tenses the suprapleural membrane; may elevate the first rib (inconstant variant).
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 Minimus receives its nerve supply from the Anterior ramus of C7 (and C8). This nerve carries fibres from spinal segment(s) C7, C8.
Because a muscle can only contract when its nerve is intact, injury to the Anterior ramus of C7 or to its spinal roots (C7, C8) can weaken or paralyse the Scalenus Minimus, impairing the movements it normally produces (tenses the suprapleural membrane). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Scalenus Minimus (the OIANS method)
Study the scalenus minimus as a variant of the scalene group whose special feature is its attachment to the suprapleural membrane over the lung apex. Fix in mind that it runs from the C7 transverse process down to the inner first rib and Sibson's fascia, which immediately explains its function of tensing that membrane and supporting the dome of the pleura rather than acting as a major neck mover.
Because it is inconstant, concentrate on the clinical relevance of its position at the thoracic inlet, close to the lower trunk of the brachial plexus and the subclavian vessels. Its supply from the anterior ramus of C7, with a possible C8 contribution, matches the segmental level of the structures it lies among, giving you a logical anchor for the nerve.
Frequently asked questions
Where is the Scalenus Minimus located?
The Scalenus Minimus is a muscle of the Neck group, located in the Head & Neck.
What is the origin of the Scalenus Minimus?
Anterior tubercle of the transverse process of C7 (variable)
What is the insertion of the Scalenus Minimus?
Inner border of the first rib and the suprapleural membrane (Sibson's fascia)
What movements does the Scalenus Minimus produce?
Tenses the suprapleural membrane; may elevate the first rib (inconstant variant)
What nerve supplies the Scalenus Minimus?
Anterior ramus of C7 (and C8)
Is the Scalenus Minimus free to study in OIANS?
The Scalenus Minimus 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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