Semispinalis Capitis
Back · Trunk
Semispinalis capitis is the large, thick, head-reaching part of the semispinalis and one of the most powerful extensors of the head. It arises from the transverse processes of the lower cervical and upper thoracic vertebrae (C7-T7) and the articular processes of the mid-cervical vertebrae (C4-C6), and its broad fibres ascend to insert on the occipital bone between the superior and inferior nuchal lines. Acting on both sides it strongly extends the head, and acting on one side it rotates the head toward the opposite side. It is innervated by the posterior (dorsal) rami of the cervical spinal nerves, and the greater occipital nerve pierces it as that nerve travels to the scalp. Its bulk makes it the dominant muscle felt on either side of the midline at the back of the neck.
Origin, Insertion, Action & Nerve
Origin
Transverse processes of C7–T7 and articular processes of C4–C6
Insertion
Occipital bone between the superior and inferior nuchal lines
Action
Extends the head and rotates it to the opposite side
Nerve
Posterior (dorsal) rami of cervical spinal nerves
Attachments explained
The Semispinalis Capitis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Transverse processes of C7–T7 and articular processes of C4–C6
Insertion
Occipital bone between the superior and inferior nuchal lines
Action & function
When the Semispinalis Capitis contracts, it produces the following movement: Extends the head and rotates it to the opposite side.
As part of the Back group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Semispinalis Capitis receives its nerve supply from the Posterior (dorsal) rami of cervical spinal nerves.
Because a muscle can only contract when its nerve is intact, injury to the Posterior can weaken or paralyse the Semispinalis Capitis, impairing the movements it normally produces (extends the head and rotates it to the opposite side). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Semispinalis Capitis (the OIANS method)
Treat semispinalis capitis as the heavyweight of the deep neck extensors: it is broad, strong, and the most conspicuous transversospinales muscle at the back of the skull. Its origin on cervical and upper thoracic transverse and articular processes and its insertion on the occipital bone between the nuchal lines explain both its powerful head extension and its contralateral rotation.
Remember the clinical hook that the greater occipital nerve pierces this muscle on its way to the scalp, which links semispinalis capitis to occipital headache and tension in the posterior neck. Contrast its opposite-side rotation and occipital attachment with longissimus capitis, which shares the head-extension role but turns the face to the same side and reaches the mastoid process instead of the occipital squama.
Frequently asked questions
Where is the Semispinalis Capitis located?
The Semispinalis Capitis is a muscle of the Back group, located in the Trunk.
What is the origin of the Semispinalis Capitis?
Transverse processes of C7–T7 and articular processes of C4–C6
What is the insertion of the Semispinalis Capitis?
Occipital bone between the superior and inferior nuchal lines
What movements does the Semispinalis Capitis produce?
Extends the head and rotates it to the opposite side
What nerve supplies the Semispinalis Capitis?
Posterior (dorsal) rami of cervical spinal nerves
Is the Semispinalis Capitis free to study in OIANS?
The Semispinalis Capitis is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Trunk is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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