Muscles which take part in the movements of the vertebral column
Flexors
When acting with their fellows of the opposite side. Rectus abdominis, infra-hyoid muscles (slightly) sterno-mastoid, external oblique, internal oblique, intercostals, scalenus anterior, psoas major and minor, longus colli, longus capitis (rectus capitis anterior major).
Extensors
When acting with their fellows of the opposite side. Sacro-spinalis, quadratus lumborum, semispinalis, multifidus, rotatores, interspinales, serrati posteriores, the splenius, and with the scapula fixed the levator scapulae and the upper fibers of the trapezius.
Muscles which help to incline the column to their own side.
Sacro-spinalis, quadratus lumborum, semispinalis, multifidus, the intercostals helping to fix the ribs, the external and internal oblique muscles, levatores costarum, serrati posteriores, the scalenes, splenius cervicis, longus colli (oblique part), rotatores, intertransversales, psoas, and with the scapula fixed the levator scapulae and the upper and lower fibers of the trapezius.
Muscles which rotate the column and turn the body to their own side
Splenius cervicis, internal oblique (the ribs being fixed), serratus posterior inferior, and with the scapula fixed the lower fibers of the trapezius.
Muscles which rotate the column and turn the body to the opposite side
Multifidus, semispinalis, external oblique, the lower oblique fibers of the longus colli, and with the scapula and humerus fixed the latissimus dorsi and trapezius.
From Morris's treatise on anatomy.
