Scalene Anatomy

Scalenus Muscles

Scalene Anterior Muscle

Scalenus Anterior

Origin: Anterior tubercles of the  transverse processes of (C3-C6)
Insertion: Scalene tubercle and cranial crest of first rib
Action: Flexion of the cervical spine, Lateral flexion of the cervical spine,
Innervation: Ventral rami of (C3-C8)
Blood Supply: Branches of the cervical artery

Primary Actions of the Scalenus Anterior

1. Flexion of the cervical spine when acting bilaterally

Agonists:

  • Longus Colli
  • Scalenus Medius

Antagonists:

  • Longissimus Cervicis
  • Iliocostalis Cervicis
  • Spinalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

2. Lateral Flexion of the cervical spine when acting unilaterally

Agonists: 

  • Scalenus Medius
  • Scalenus Posterior
  • Iliocostalis cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Antagonists: same muscles opposite side

  • Scalenus Medius
  • Scalenus Posterior
  • Iliocostalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Secondary Actions:

1. Assists with contralateral rotation of the cervical spine when acting unilaterally

Agonists:

  • Semispinalis Cervicis
  • Multifidus,

Antagonists: same muscles on opposite side

  • Semispinalis Cervicis
  • Multifidus

2. Assists with forced inspiration by elevating first rib

Agonists: 

  • Serratus Posterior Superior
  • Levatores Costarum Brevis
  • Levatores Costarum Longi

Antagonist:

  • Serratus Posterior Inferior
  • Transversus Abdominis
Scalene Medius Muscle

Scalenus Medius

Origin: Posterior tubercles of the transverse processes of (C2-C7)
Insertion: Cranial surface of the first rib
Action: Flexion of the cervical spine, Lateral flexion of cervical spine
Innervation: Ventral rami of (C3-C8)
Blood Supply: Branches of the cervical artery

Primary Actions of the Scalenus Medius

1. Flexion of the cervical spine when acting bilaterally

Agonists:

  • Longus Colli
  • Scalenus Anterior

Antagonists:

  • Longissimus Cervicis
  • Iliocostalis Cervicis
  • Spinalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

2. Lateral Flexion of the cervical spine when acting unilaterally

Agonists: 

  • Scalenus Anterior
  • Scalenus Posterior
  • Iliocostalis cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Antagonists: same muscles opposite side

  • Scalenus Medius
  • Scalenus Posterior
  • Iliocostalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Secondary Actions:

3. Assists with contralateral rotation of the cervical spine when acting unilaterally

Agonists:

  • Semispinalis Cervicis
  • Multifidus,

Antagonists: same muscles on opposite side

  • Semispinalis Cervicis
  • Multifidus

4. Assists with forced inspiration by elevating first rib

Agonists: 

  • Serratus Posterior Superior
  • Levatores Costarum Brevis
  • Levatores Costarum Longi

Antagonist:

  • Serratus Posterior Inferior
  • Transversus Abdominis
Scalene Posterior Muscle

Scalenus Posterior

Origin: By tendons from the posterior tubercles of  the transverse processes of (C4–C6)
Insertion: Outer surface of 2nd rib
Action: Lateral flexion of the neck
Innervation: Ventral rami of (C3-C8)
Blood Supply: Branches of the cervical artery

Primary Actions of the Scalenus Posterior

Primary Actions:

1. Lateral flexion of the cervical spine when acting unilaterally

Agonists: 

  • Scalenus Anterior
  • Scalenus Medius
  • Iliocostalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Antagonists: same muscles on opposite side

  • Scalenus Anterior
  • Scalenus Medius
  • Iliocostalis Cervicis
  • Splenius Cervicis
  • Semispinalis Cervicis

Secondary Actions:

2. Assists with contralateral rotation of the cervical spine when acting unilaterally

Agonists:

  • Semispinalis Cervicis
  • Multifidus

Antagonists: same muscles on opposite side

  • Semispinalis Cervicis
  • Multifidus

4. Assists with forced inspiration by elevating the second rib

Agonists: 

  • Serratus Posterior Superior
  • Levatores Costarum Breves
  • Levatores Costarum Longi

Antagonists: None

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