Superficial layer

Splenius (splenius capitis, splenius cervicis)

Intermediate layer

Erector spinae (iliocostalis, longissimus, spinalis)

Deep layer

Transversospinales (semispinalis, multifidus, rotatores)

Deepest layer:

Segmental muscles (levatores costarum, interspinales and intertransversarii