Scalene Muscles: Innervation, Function, Action, Location

Scalene Muscles: Innervation, Function, Action, Location

Describe the origin, insertion, nerve supply, actions and relations of Scalenus Anterior Muscle.
Answer.

Scalenus Anterior Muscle Origin

From anterior tubercles of transverse processes of C3 to C6 vertebrae.

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Scalenus Anterior Muscle Insertion

Into scalene tubercle on the inner border of 1st rib.

Scalenus Anterior Muscle Nerve supply

By ventral rami of C4 to C6 spinal nerves.

Scalenus Anterior Muscle Actions

• Acting from below, it bends the neck forwards and laterally.
• Acting from above, it elevates the 1st rib and thus acts as an accessory muscle of respiration.

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Scalenus Anterior Muscle Relations

It is key muscle at the root of neck because many important structures are related to it.

Scalenus Anterior Muscle Anterior relations:

• Two nerves: Phrenic nerve and descendens cervicalis
• Two arteries: Transverse cervical and suprascapular
• Two veins: Anterior jugular and subclavian
• Two muscles: Inferior belly of omohyoid and sternocleidomastoid

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Scalenus Anterior Muscle Posterior relations:

• Branchial plexus (lower trunk)
• Subclavian artery (second part)
• Cervical pleura
• Suprapleural membrane

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Scalenus Anterior Muscle Lateral:

Trunks of brachial plexus

Scalenus Anterior Muscle Medial:

Thyrocervical trunk

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Scalenus Anterior Muscle Applied anatomy

• Scalene syndrome occurs if roots of brachial plexus and subclavian artery are compressed between scalenus anterior muscle and first rib.
• Cervical rib syndrome occurs when cervical rib passing through a gap between scalenus anterior and scalenus medius muscles compressing lower trunk of brachial plexus and subclavian artery.
• Clinically these syndromes present as:
• Tingling and numbness in the little finger and medial half of ring fingers due to involvement of T8 and T1.
• Absence of radial pulse due to compression of subclavian artery.