Head and Neck Anatomy: Muscles of the Back of Neck

The muscles of the entire back can be grouped into the following four layers from superﬁcial to the deeper plane.

1. Trapezius and latissimus dorsi

2. Levator scapulae, rhomboids (two), serratus posterior superior, Splenius

3. a. Erector spinae or sacrospinalis

b. semispinalis

4. Multiﬁdus, rotatores, interspinales, intertransversii and suboccipital muscles

Splenius muscles are two in number.

These are splenius cervicis and splenius capitis.

These cover the deeper muscles like a bandage

Origin: From lower half of ligamentum nuchae and spines of upper 5 thoracic vertebrae.

These curve in a half spiral fashion and separate into splenius cervicis and splenius capitis.

Splenius cervicis gets inserted into the posterior tubercles of transverse processes of C1-C4 vertebrae.

Splenius capitis forms the ﬂoor of the posterior triangle and gets inserted into the mastoid process beneath the sternocleidomastoid muscle

It is supplied by dorsal rami of C1-C6 nerves.

Suboccipital Muscles

1. Rectus Capitis Posterior Major

Origin - Spine of axis

Insertion - Lateral part of the area below the inferior nuchal line

Nerve Supply - Suboccipital nerve or dorsal ramus Cl

Action

1. Mainly postural

2. Acting alone it turns the chin to the same side

3. Acting together the two muscles extend the head

Rectus capitis posterior minor

Origin - Posterior tubercle of atlas

Insertion - Medial part of the area below the inferior nuchal line

Nerve Supply - Suboccipital nerve or dorsal ramus Cl

Actions

1. Mainly postural

2. Extends the head

Obliquus capitis superior( superior oblique)

Origin: Transverse process of atlas

Insertion: Lateral area between the nuchal lines

Nerve Supply: Suboccipital nerve or dorsal ramus Cl

Actions:

1. Mainly postural

2. Extends the head

3. Flexes the head laterally

Obliquus capitis inferior (inferior oblique)

Orgin: Spine of axis

Insertion: Transverse process of atlas

Nerve Supply: Suboccipital nerve or dorsal ramus Cl

Actions:

1. Mainly postural

2. Turns chin to the same side

Suboccipital Triangle

Boundaries

Superomedially

Rectus capitis posterior major muscle supplemented by the rectus capitis posterior minor.

Superolaterally

Superior oblique capitis muscle.

lnferiorly

Inferior oblique capitis muscle.

Roof -

1. Skin

2. Superﬁcial Fascia with greater & third occipital Nerve

3. Trapezius & Sternocleidomastoid

4. Splenius capitis

5. Semispinalis capitis & Longissimus capitis

Floor

1. Posterior arch of atlas.

2. Posterior atlanto-occipital membrane.

Contents

1 Third part of vertebral artery.

2 Dorsal ramus of nerve C1 - suboccipital nerve.

3 Suboccipital plexus of veins.

Applied Anatomy:

1. Neck rigidity, seen in cases with meningitis, is due to spasm of the extensor muscles. This is caused by irritation of the nerve roots during their passage through the subarachnoid space which is infected.

Passive ﬂexion of neck and straight leg raising test cause pain as the nerves are stretched

2. Cisternal puncture is done when lumbar puncture fails.

The patient either sits up or lies down in the left lateral position.

A needle is introduced in the midline above the spine of axis in forward and upward direction parallel to an imaginary line extending from external acoustic meatus to nasion.

It passes through the posterior atlanto-occipital membrane between the posterior arch of atlas and the posterior margin of foramen magnum. The needle enters the cerebellomedullary cistern and small amount of CSF is withdrawn.

3. Neurosurgeons approach the posterior cranial fossa through this region.