Semispinalis Capitis Anatomy

Semispinalis Capitis O, I, A

Origin:  Articular processes of vertebrae C4-C7, transverse processes of vertebrae T1-T6
Insertion: Between superior and inferior nuchal lines of occipital bone
Actions:  Extension of the head and cervical spine
Innervation:  Descending branches of greater occipital nerve (C2) and spinal nerve C3
Blood Supply: Descending branches of the occipital artery

Primary Actions of the Semispinalis Capitis

 1.  Extension of the head and cervical spine when acting bilaterally

Agonists:

  • Longissimus capitis
  • Spinalis capitis
  • Splenius capitis
  • Sternocleidomastoid (posterior fibers)
  Antagonists:
  • Longus capitis
  • Sternocleidomastoid (anterior fibers)

2.  Contralateral rotation of the head and cervical spine when acting unilaterally

Agonists:

  • Trapezius (upper part)
  • Sternocleidomastoid
  Antagonists: same muscles on the contralateral side

  • Trapezius (upper part)
  • Sternocleidomastoid

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Secondary Actions of the Semispinalis Capitis

2. Assists with lateral flexion of the head and cervical spine when acting unilaterally

Agonists:

  • Splenius capitis
  • Sternocleidomastoid

  Antagonists: same muscles on contralateral side

  • Splenius capitis
  • Sternocleidomastoid