Exploring The Erector Spinae Muscles

What are the erector spinae muscles?

Erector Spinae Muscles

The erector spinae muscles are a group of muscles that belong to an even broader group of muscles called the paraspinal muscles. You can get a sense from breaking down the name where this larger group of muscles is located. ‘Para’ means alongside or beside. ‘Spinal’, of course, refers to the spine. So, the erector spinae muscles belong to a bigger group of muscles that are all located along the spine. Other muscles included in the paraspinal muscle group include the rotatores and the multifidi.

The erector spinae muscles include three main muscles which themselves can also be divided into sections. The erector spinae muscles include: iliocostalis, longissimus, and spinalis. Each of these muscles can be divided into three sections. We have iliocostalis cervicis, iliocostalis thoracis, and iliocostalis lumborum. We have longissimus capitis, longissimus cervicis, and longissimus thoracis. Finally, we have spinalis capitis, spinalis cervicis, and spinalis thoracis.

Where are the erector spinae muscles?

As we described above, most generally we find the erector spinae muscles alongside the spine. The spinalis muscles are most medially located. That is, they are closest to the spine. Next to spinalis we find the longissimus muscles. The iliocostalis are located most laterally of the erector spinae muscles.

Let’s break each of these muscles down into their three smaller muscles and look at their attachments.

Muscle origins

  • Spinalis capitis: spinous processes of C7 to about T2 (but often hard to differentiate from semispinalis capitis)
  • Spinalis cervicis: nuchal ligament and spinous processes C6 or C7
  • Spinalis thoracis: spinous processes T10 to L3
  • Longissimus capitis: transverse processes of T1 to T5 and articular processes of C5 to C7
  • Longissimus cervicis: transverse processes of T1 to T5
  • Longissimus thoracis: sacrum, spinous and transverse processes of all lumbar and thoracic vertebrae
  • Iliocostalis cervicis: angle of ribs 3 through 6
  • Iliocostalis thoracis: superior border of the lower 6 ribs
  • Iliocostalis lumborum: medial iliac crest, sacrum, and spinous processes of the lumbar spine

Muscle insertions

  • Spinalis capitis: lateral nuchal line (but often hard to differentiate from semispinalis capitis)
  • Spinalis cervicis: spinous processes C2 to C4
  • Spinalis thoracis: spinous processes T2 to T8
  • Longissimus capitis: posterior mastoid process
  • Longissimus cervicis: transverse processes of C2 to C6
  • Longissimus thoracis: transverse processes of all thoracic vertebrae
  • Iliocostalis cervicis: transverse processes C4 to C6
  • Iliocostalis thoracis: superior border of the upper 6 ribs and transverse process of C7
  • Iliocostalis lumborum: inferior border of the lower 6 or 7 ribs

Muscle actions

  • All of the erector spinae muscles work bilaterally to extend the spine.
  • Longissimus thoracis and longissimus cervicis also function unilaterally to laterally flex the spine to the same side. 
  • Longissimus capitis functions unilaterally to rotate the head to the same side.
  • The iliocostalis muscles and spinalis capitis work unilaterally to laterally flex the spine to the same side.

While the erector spinae muscle group is very important for extending the spine, there are also many other muscles that contribute to moving the spine in different ways. If you want to learn more about other muscles that move the spine check out our post: Exploring The Spine!

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