The muscles of the back

The deeper layers of the muscles of the back are known as the true or autochthonous back muscles. A highly differentiated complex of muscle groups, they also connect the spinous and transverse processes of the vertebrae.
The interplay of all these muscle groups facilitates the extension, flexion, rotation and lateral movement of the back.
The musculus erector spinae (4), the sacrospinalis muscle or ”extensor of the back” is an important component consisting of a number of individual muscles and extending from the pelvis to the head. Additional systems of muscles can be differentiated deep in the muscles of the back:

• Muscles of the spinal system, the origins and insertions of which are at the vertebral spinous processes, such as the musculus spinalis (6)
• Muscles of the transversospinal system connecting the transverse processes to the spinous processes of the vertebrae. The musculi rotatores thoracis (8) and musculi multifidi (7) are typical of this group. Finally, there are the
• Muscles of the intertransverse system that connect the transverse processes of the vertebrae to one another (e.g.: musculi intertransversarii (9)).