Semispinalis Cervicis Anatomy

Semispinalis Cervicis O, I, A

Origin: By fleshy and tendinous fibers to the transverse processes of T1 to T6
Insertion: Spinous processes of C2 to C5, spanning four to six levels between attachment points
Actions: Extension, lateral flexion and rotation of the spine.
Innervation: Dorsal primary rami of C3 to C5
Blood Supply: Descending branches of the occipital artery and the superior intercostal artery, via the dorsal rami of the upper two posterior intercostal arteries

Primary Actions of the Semispinalis Cervicis

1.  Extension of the cervical spine when acting bilaterally

  Agonists:

  • Iliocostalis cervicis
  • Longissimus cervicis
  • Spinalis cervicis
  • Splenius cervicis

  Antagonists:

  • Longus Colli (superior oblique and inferior oblique)
  • External Oblique
  • Internal Oblique
  • Anterior Scalene
  • Middle Scalene

2. Lateral flexion of the cervical spine when acting unilaterally

Agonists:

  • Anterior Scalene
  • Middle Scalene
  • Posterior Scalene
  • Iliocostalis Cervicis
  • Splenius Cervicis

Antagonists: Same muscles on contralateral side

  • Anterior Scalene
  • Middle Scalene
  • Posterior Scalene
  • Iliocostalis Cervicis
  • Splenius Cervicis

3. Contralateral rotation of the cervical spine when acting unilaterally

Agonists:

  • Multifidus

Antagonists: Same muscles on contralateral side

  • Multifidus

4. Extension of the thoracic spine when acting bilaterally

Agonists:

  • Iliocostalis Cervicis,
  • Iliocostalis Thoracis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • Spinalis Thoracis
  • Semispinalis Thoracis

Antagonists:

  • Rectus abdominis

5. Contralateral rotation of the trunk when acting unilaterally

Agonists:

  • Semispinalis thoracis
  • Multifidus
  • External oblique

Antagonists: Same muscles on contralateral side

  • Semispinalis thoracis
  • Multifidus
  • External oblique

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Secondary Actions of the Semispinalis Cervicis

1. Assists with lateral flexion of the thoracic spine when acting unilaterally

  Agonists:

  • Iliocostalis Cervicis
  • Iliocostalis Thoracis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • External Oblique
  • Internal Oblique

  Antagonists: Same muscles on contralateral side

  • Iliocostalis Cervicis
  • Iliocostalis Thoracis
  • Iliocostalis Lumborum
  • Longissimus Cervicis
  • Longissimus Thoracis
  • External Oblique
  • Internal Oblique