Muscles - Suboccipital

Question 1

Where are these muscles found?

Answer 1

There are four sub-occipital muscles situated underneath the occipital bone. They are also located within the suboccipital compartment of the neck, deep to the sternocleidomastoid, trapezius, splenius and semispinalis muscles.

Question 2

What nerve innervates these muscles?

Answer 2

Sub-occipital nerve, dorsal ramus of C1.

Question 3

What is the function of these muscles?

Answer 3

Extends and rotate the head.

Question 4

What are the four sub-occiptal muscles?

Answer 4

1) Rectus capitis posterior major
2) Rectus capitis posterior minor
3) Obliquus capitis inferior
4) Obliquus capitis superior

Question 5

Rectus capitis posterior major

Answer 5

Larger of the rectus capitis muscles. Located laterally to the rectus capitis posterior minor muscle.

Origin - spinous process of the axis (C2)

Insertion - lateral part of the inferior nuchal line of the occipital bone

Action - extension and rotation of the head

Innervation - sub-occipital nerve (dorsal ramus of C1)

Question 6

Rectus capitis posterior minor

Answer 6

The most medial of the sub-occipital muscles. There is a connective tissue bridge between this muscle and the dura mater - which may play a role in cervicogenic headaches (pain referred from the source of the neck to the head).

Origin - posterior tubercle (rudimentary spinous process) of atlas (C1)

Insertion - medial part of the inferior nuchal line of the occipital bone.

Action - extension of the head

Innervation - sub-occipital nerve (dorsal ramus of C1)

Question 7

Obliquus capitis inferior

Answer 7

Most inferiorly positioned of the sub-occipital muscles. It also has no attachment to the cranium.

Origin - spinous process of axis (C2)

Insertion - transverse process of atlas (C1)

Action - extension and rotation of the head

Innervation - sub-occipital nerve (dorsal ramus of C1)

Question 8

Obliquus capitis superior

Answer 8

Located laterally in the sub-occipital compartment.

Origin - transverse process of the atlas (C1)

Insertion - betweeen the inferior and superior nuchal line of the occipital bone.

Actions - Extension of the head

Innervation - sub-occipital nerve (dorsal ramus of C1)

Question 9

Clinical relevance: sub-occipital triangle

Answer 9

It contains the vertebral artery, sub-occipital venous plexus, and sub-occipital nerve.

This is an area border by three of the sub-occupital muscles:

Superomedially - rectus capitis posterior major,

Inferiorly - obliquus capitis inferior

Superolaterally - obliquus capitis superior.

Roof - semispinalis capitus

Floor - posterior atlanto-occipital membrane and posterior arch of the C1 atlas vertebra.