The name, erector spinae, refers to the function of these muscles. They are a powerful group of muscles whose job is to keep the spine erect, or upright. The word erector then refers to erect, or upright. The word spinae refers to the spine.
The erector spinae muscles are really three muscles: spinalis, longissimus, and iliocostalis. Each of these three muscles can be further subdivided into additional smaller muscles based on the region of the spine they are in.
Spinalis comes from the Latin word spina which means “thorn”. It refers to the bumpy projections that you can feel along the length of the spine, the spinous processes.
Longissimus is the Latin word for “longest”.
The word iliocostalis comes from the Latin words ilium, which refers to the large pelvic bone, and costa which means “rib”.
Where do the erector spinae muscles attach?
Spinalis is the most medial of the erector spinae muscles. It can be further subdivided into three sections, the spinalis thoracis, spinalis cervicis, and spinalis capitis.
The longissimus is the middle muscle of the erector spinae group. It can be further subdivided into three muscles: the longissimus thoracis, longissimus cervicis, and longissimus capitis muscles.
Iliocostalis is the most lateral of the muscles in the erector spinae group. It can be further subdivided into two smaller muscles, the iliocostalis lumborum and iliocostalis cervicis.
- Spinalis thoracis originates on the spinous processes from about T10 – L3.
- Spinalis cervicis originates on the lower part of the nuchal ligament and spinous processes of C6 or 7.
- Longissimus thoracis originates on the sacrum and the spinous and transverse processes of all lumbar and thoracic vertebrae.
- Longissimus cervicis originates on the transverse processes of T1 – T5.
- Longissimus capitis originates on the transverse processes of of T1 – T5 and the articular processes of C5 – C7.
- Iliocostalis lumborum originates on the medial aspect of the iliac crest, the sacrum, and spinous processes of the lumbar vertebrae.
- Iliocostalis thoracis originates on the superior border of the lower 6 ribs, just medial to the iliocostalis lumborum.
- Iliocostalis cervicis originates on the angle of the ribs 3 – 6.
- Spinalis thoracis inserts on the spinous processes from about T2 – T8.
- Spinalis cervicis inserts on the spinous processes of C2 and sometimes C3 and C4.
- Longissimus thoracis inserts on the transverse processes of all the thoracic vertebrae.
- Longissimus cervicis inserts on the transverse processes of C2 – C6.
- Longissimus capitis inserts on the posterior part of the mastoid process.
- Iliocostalis lumborum inserts on the inferior borders of the lower 6 or 7 ribs.
- Iliocostalis thoracis inserts on the superior border of the upper 6 ribs and the transverse process of C7.
- Iliocostalis cervicis inserts on the transverse processes of C4 – C6.
What actions do the erector spinae muscles do?
Spinalis thoracis and spinalis cervicis function bilaterally to extend their sections of the spine.
Longissimus thoracis, longissimus cervicis, and longissimus capitis all function bilaterally to extend their portions of the spine and/or head. Longissimus thoracis and longissimus cervicis also laterally flex the spine to the same side. Longissimus capitis can rotate the head to the same side.
Iliocostalis lumborum, iliocostalis thoracis, and iliocostalis cervicis all function bilaterally to extend the spine. Unilaterally they function to laterally flex the spine to the same side.