Scalenus Muscles
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, rotation of the cervical spine, Elevation of the first rib
Innervation: Anterior branches of the cervical nerves C5 to C7.
Blood Supply: Ascending cervical branch of the inferior thyroid 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
Scalenus Medius
Origin: Posterior tubercles of the transverse processes of (C2-C7)
Insertion: Upper surface of the first rib
Action: Flexion of the cervical spine, Lateral flexion of cervical spine, elevation of the first rib
Innervation: Anterior rami of cervical spinal nerves (C3-C8)
Blood Supply: Branches of the ascending 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
Scalenus Posterior
Origin: Posterior tubercles of the transverse processes of (C2–C7)
Insertion: Outer surface of 2nd rib
Action: Flexion of the cervical spine, Lateral flexion of the cervical spine, Rotation of the cervical spine, Elevation of the 2nd rib.
Innervation: Anterior rami of (C5-C7)
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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For beginning and intermediary anatomy . Muscle overlays on the human body. Excellent visuals!