Semispinalis cervicis muscle
Semispinalis cervicis is a muscle of the back. Along with the semispinalis capitis and thoracis it comprises a long semispinalis muscle. This muscle belongs to the spinotransverse group of deep back muscles, along with the rotatores and multifidus muscles.
The main anatomical feature of the semispinalis muscle, and of the semispinalis cervicis, is that it attaches between the spinous and transverse processes of vertebrae, bridging five to six vertebral levels along its course.
Semispinalis cervicis acts in synergy with its capitis and thoracis counterparts. Their conjoint function facilitates the movements of the vertebral column; extension, lateral flexion and rotation of the head, cervical and thoracic spines.
This article will discuss the anatomy and function of the semispinalis cervicis muscle.
|Origin||Transverse processes of vertebrae T1-T6|
|Insertion||Spinous processes of vertebrae C2-C5|
Bilateral contraction - Extension of head, cervical and thoracic spine
Unilateral contraction - Lateral flexion of head, cervical and thoracic spine (ipsilateral), rotation of head, cervical and thoracic spine (contralateral)
|Innervation||Medial branches of posterior rami of spinal nerves|
|Blood supply||Occipital, deep cervical and vertebral arteries|
Semispinalis cervicis originates from the transverse processes of vertebrae T1-T6. The slender fascicles of this muscle span over the thoracic and cervical regions of the back to finally insert onto the posterior surfaces of spinous processes of vertebrae C2-C5. The muscle fibers span in a laminated fashion, so that those originating from T1 insert to the C2, while those stemming from T6 insert to the C5.
The dorsal and lateral aspects of the semispinalis cervicis lie deep to the semispinalis capitis muscle. On its course, the muscle covers the dorsal surface of multifidus cervicis and thoracis muscles, while medially are the bodies of cervical and thoracic vertebrae. Semispinalis cervicis is innervated by the medial branches of posterior rami of spinal nerves, while its arterial supply comes from the occipital, deep cervical and vertebral arteries.
The function of semispinalis cervicis is to help the head and neck extensors to extend the head at the neck when contracting bilaterally. On the other hand, its unilateral contraction aids the same muscles to perform the ipsilateral lateral flexion and contralateral rotation of the head, cervical and thoracic spines.