Quick Facts
Origin: Transverse processes of C2-C7 vertebrae.
Insertion: Superior surface of first rib.
Action: Laterally flexes neck; elevates first rib.
Innervation: Anterior rami of third to eighth cervical nerves (C3-C8).
Arterial Supply: Ascending cervical artery.
Related parts of the anatomy
Origin
The scalenus medius muscle arises from the transverse process of second cervical vertebra (axis) and the posterior tubercles of the transverse processes of the third to seventh cervical vertebrae (C3-C7). It commonly has an additional slip which attaches to the first cervical vertebra (atlas).
Insertion
The scalenus medius muscle inserts into the superior surface of the first rib, specifically, between the tubercle of the rib and the groove for the subclavian artery.
Key Features & Anatomical Relations
The scalenus medius muscle is crossed anteriorly by the omohyoid muscle as it runs posteriorly towards the scapula. It is separated from the scalenus anterior muscle by the subclavian artery and the brachial plexus.
Actions
The scalenus medius muscle is involved in multiple actions:
- during unilateral contraction, it laterally flexes the neck to the same side at the cervical vertebral joints;
- it elevates the first rib and can act as an accessory muscle of inspiration (Standring, 2016).
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
