Deep structures of the neck: Prevertebral muscles

The neck is the anatomical region between the base of the cranium superiorly and the clavicles inferiorly and it joins the head to the trunk and limbs, serving as a major conduit for structures passing between them.

The neck contains superficial structures, located in the anterior and posterior triangles and deep structures, like the cervical viscera and the prevertebral muscles.

Now, the prevertebral muscles are deep to the prevertebral layer of the deep cervical fascia and they are divided into anterior prevertebral muscles and lateral prevertebral muscles.

The anterior prevertebral muscles are located directly posterior to the retropharyngeal space and medial to the neurovascular plane of the cervical plexus, brachial plexus and subclavian artery, and they are represented by longus colli, longus capitis, rectus capitis anterior and anterior scalene muscles.

Now, the longus colli originates from the bodies of C5 to T3 vertebrae and the transverse processes of C3 to C5 vertebrae.

It inserts onto the anterior tubercle of the C1 vertebra, the bodies of the C2 to C4 vertebrae and the transverse processes of C3 to C6 vertebrae.

It’s innervated by the anterior rami of C2 to C6 spinal nerves When it contracts bilaterally, it produces flexion of the neck and when it contracts unilaterally it produces rotation to the opposite side.

Next, there’s the longus capitis, which originates from the anterior tubercles of the transverse processes of C3 through C6 and inserts onto the basilar part of occipital bone.

It’s innervated by the anterior rami of spinal nerves C1 through C3 and its contraction results in flexion of the head at the atlanto-occipital joint.

Next, the rectus capitis anterior originates from the anterior surface of the lateral mass of the atlas, which is the first cervical vertebra, and inserts onto the base of the cranium, anterior to the occipital condyles.

It’s innervated by branches from the loop between C1 and C2 spinal nerves and its contraction also results in flexion of the head at the atlanto-occipital joint.

Finally, the anterior scalene muscle originates from the anterior tubercles of the transverse processes of the C3 to C6 vertebrae and inserts onto the first rib.

It’s innervated by the anterior rami of spinal nerves C4 to C6. It functions to elevate the first rib during forced inspiration, and when the rib is fixed, bilateral contraction produces flexion of the neck and unilateral contraction produces lateral flexion of the neck.Next up, there are the lateral prevertebral muscles, located posterior to the neurovascular plane of the cervical and brachial plexuses and subclavian artery.

These are the rectus capitis lateralis, middle and posterior scalene muscles, levator scapulae, and splenius capitis. Rectus capitis lateralis originates from the transverse process of the atlas and inserts onto the jugular process of the occipital bone.

It’s innervated by branches from the loop between C1 and C2 spinal nerves and when it contracts, it stabilizes and flexes the atlanto-occipital joint.

Next, the middle scalene muscle originates from the posterior tubercles of transverse processes of C3 to C7 vertebrae while the insertion is on the superior surface of the first rib, posterior to the groove for subclavian artery.

It’s innervated by anterior rami of the C3 to C7 spinal nerves. As with anterior scalene, it elevates the first rib during forced inspiration, and when the rib is fixed, bilateral contraction produces flexion of the neck and unilateral contraction produces lateral flexion of the neck.The posterior scalene muscle originates from the posterior tubercles of the transverse processes of C5 to C7 and inserts inferiorly on the external border of the second rib.

It’s innervated by the anterior rami of spinal nerves C7 and C8. The posterior scalene elevates the second rib during forced inspiration, and - just like the other scalenes - when this rib is fixed, bilateral contraction produces flexion of the neck and unilateral contraction produces lateral flexion of the neck.

The anterior scalene, middle scalene, and posterior scalene are considered accessory muscles of inspiration because, during deep inhalations, they lift the ribs they are attached to, which contributes to increasing the intrathoracic volume.Next, the levator scapulae originates from the posterior tubercles of the transverse processes of the C1 to C4 vertebrae and inserts onto the superior part of the medial border of the scapula.

It’s innervated by the anterior rami of C3 andC4, and the dorsal scapular nerve which mainly derives from C5, as well as potentially C4.

It elevates the scapula and produces downward rotation of the scapula, which causes the glenoid cavity to tilt inferiorly.

The splenius capitis originates from the inferior half of the nuchal ligament and the spinous processes of C7 to T4. It inserts onto the mastoid process of temporal bone and the lateral third of the superior nuchal line.

It’s innervated by the posterior rami of the middle cervical spinal nerves and it produces lateral flexion and rotation of the head to the same side when it acts unilaterally, as well as extension of the head and neck when acting bilaterally.

Okay, time for a quick break! Try to identify the anterior and lateral prevertebral muscles.

##SummaryOk, a quick recap. The deep structures of the neck include the prevertebral muscles which are divided into anterior prevertebral muscles represented by longus colli, longus capitis, rectus capitis anterior and anterior scalene muscles and lateral prevertebral muscles which are represented by rectus capitis lateralis, middle scalene muscle, posterior scalene muscle,