Paravertebral Muscles - The Scalenus Anterior muscle| Attachments | Nerve supply| Action | Relations

Scalenus anterior
Origin
Anterior tubercles of transverse processes
of cervical vertebrae 3, 4, 5 and 6
Insertion
Scalene tubercle and adjoining ridge on the superior surface of the first rib (between subclavian artery and vein)
Nerve Supply
Ventral rami of nerves C4-C6
Action
a. Anterolateral flexion of cervical spine
b. Rotates cervical spine to opposite side
c. Elevates the first rib during inspiration
d. Stabilises the neck along with other muscles
Relations of scalenus anterior.
The scalenus anterior is a key muscle of the lower part of the neck because of its intimate relations to many important structures in this region. It is a useful surgical landmark.
Anterior:
a. Phrenic nerve covered by prevertebral fascia.
b. Lateral part of carotid sheath containing the internal jugular vein.
c. Sternocleidomastoid.
d. Clavicle.
Posterior:
a. Brachial plexus.
b. Subclavian artery.
c. Scalenus medius.
d. Cervical pleura covered by the suprapleural membrane
The medial border of the muscle is related:
a. In its lower part to an inverted ‘V'-shaped interval, formed by the diverging borders of the scalenus anterior and the longus colli.
This interval contains many important structures as follows:
i. Vertebral vessels running vertically from the base to the apex of this space.
ii. Inferior thyroid artery arching medially at the level of the 6th cervical transverse process.
iii. Sympathetic trunk.
iv. The first part of the subclavian artery traverses the lower part of the gap.
v. On the left side, the thoracic duct arches laterally at the level of the seventh cervical transverse process
vi. The carotid sheath covers all the structures mentioned above.
vii. The sternocleidomastoid covers the carotid sheath
.b. In its upper part, the scalenus anterior is separated from the longus capitis by the ascending cervical artery. The lateral border of the muscle is related to the trunks of the brachial plexus and the subclavian artery which emerges at this border and enter the posterior triangle










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