The semispinalis muscles are the most superficial layer of a group of muscles called the transversospinal muscles. The layers of the transversospinal muscles contribute to spinal movements. As the name suggests, they run between the transverse processes and the spinous processes of the spinal vertebrae. The deepest muscles in this group are the rotatores and the middle layer are the multifidus muscles which we covered in a previous article. In this article, we’ll take a look at the superficial layer, the semispinalis capitis, cervicis, and thoracis.
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What do the names semispinalis capitis, semispinalis cervicis, and semispinalis thoracis mean?
The word semispinalis breaks down into two parts, semi and spinalis. Semi means half and spinalis means thorn. In this case, the “thorn” that the name refers to is the spinous process, which is the bony protrusion that sticks out from the back of each of our vertebrae. Therefore, you can understand from the name that this is a group of muscles that attach at one end to the spinous processes. Similarly, the second part of the name for each of these three muscles describes where along the spine it’s located. The word capitis refers to the head. The word cervicis refers to the cervical spine, or neck. And, the word thoracis refers to the thoracic section of the spine.
Where do these muscles attach?
Each semispinalis muscle is actually two halves of a pair of muscles. We have a semispinalis capitis, cervicis, and thoracis on both the right and left sides of our spine. Each section of a semispinalis muscle spans five to six vertebrae.
Origin
Semispinalis capitis originates from the transverse processes of T1 to T6 or T7 and the articular processes of C3 or C4 to C6 or C7. The semispinalis cervicis originates from the transverse processes of T1 to T6. Semispinalis thoracis originates from the transverse processes of T6 to T10.
Insertion
Semispinalis capitis inserts between the superior and inferior nuchal lines of the occipital bone just posterior to the inferior attachment of the suboccipital muscles. The semispinalis cervicis inserts onto the spinous processes of C2 to C5. The semispinalis capitis is deep to the splenius capitis. However, semispinalis capitis covers the most superior section of semispinalis cervicis. Semispinalis thoracis inserts onto the spinous processes of C6 to T4. The semispinalis thoracis is medial to the erector spinae muscles.
Semispinalis capitis muscle
What actions do the semispinalis muscles do?
Most generally, these muscles work together to bilaterally extend the spine. Unilaterally they contribute to lateral flexion of the same side and rotation to the opposite side. More specifically, semispinalis capitis contributes to extension, lateral flexion, and rotation of the head on the neck as well as movement of the cervical spine (neck). Semispinalis cervicis and thoracis contribute to extension, lateral flexion, and rotation of the cervical and thoracic spine.
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Poses where these muscles contract
These muscles contract bilaterally every time we extend our spine. For example, in an upward dog, we contract all three semispinalis muscles.
Similarly, in a pose like ustrasana (camel), we contract semispinalis capitis, cervicis, and thoracis when we extend our spine and head.
Poses where these muscles are lengthened
In contrast, we lengthen the semispinalis muscles when we flex the spine and the head.
