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Erector spinae muscle

Synonym: autochthonous muscles of the back
German: Musculus erector spinae

1 Definition

The erector spinae muscle is defined as the muscles of the back being laid up aound the spinal column, which, in contrast to many other muscle groups, has not migrated during embryonic development, but it has developed next to the spinal column and not changed its place.

2 Position

The autochthonous muscles of the back lie in an osteofibrous tunnel that is formed by the thoracolumbar fascia, the lamina of the vertebral arches, as well as the spinous and transverse processes of the vertebrae and, partly, by the ribs.

3 Muscle groups of the erector spinae muscle

The autochthonous muscles of the back are divided into a medial and a lateral tract. The exact division of the muscles of the back into the individual cord systems is not consistent in anatomic literature, which is not surprising considering the complexity of the muscles of the back.

3.1 Medial tract

This tract comprises:

3.1.1 Interspinal and spinal system

These muscles connect the spinous processes of neighboring vertebrae.

3.1.2 Transversospinal system

These muscles pass from the transverse process of one vertebra to the spinous process of another, more proximal vertebra or to the back of the head, while they can leap some segments. They comprise:

3.2 Lateral tract

This tract comprises:

3.2.1 Intertransversal system

These muscles connect the transverse processes of neighboring vertebrae. They comprise:

3.2.2 Sacrospinal system

The sacrum, the spinous processes of the lumbar vertebrae, the iliac crest and the thoracolumbar fascia serve as origin for these muscles. They can leap segments and insert in the ribs and the spinal column.

3.2.3 Spinotranservse system

These muscles pass from the spinous processes to the transverse processes of proximal vertebrae. They comprise:

3.2.4 Rib-lifting muscles

These muscles draw - in contrast to their name - the vertebral bodies downwards. Thus, they cause lateral flexion with unilateral contraction, and dorsal extension with bilateral contraction.

4 Function

The main function of the autochtonous muscles of the back lies in the erection of the spinal column and in keeping the head upright. With a unilateral contraction, especially of the medial and lateral tract, these muscle groups can also turn the spinal column or incline it to the side.

5 Innervation

The innervation is provided by the dorsal branches of the spinal nerves, which divide into a medial and lateral branch. The medial tract is innervated by the medial branch, the lateral tract by the lateral branch.

6 Fasciae

The autochtonous muscles of the back in the thoracic and lumbar region lie between the superficial and the profound leaf of the thoracolumbar fascia, which also serves as point of origin for some muscles. In the cervical region, it is surrounded by the nuchal fascia, which separates the autochtonous muscles from the muscles immigrated during embryonic development.

7 Clinical presentation

Tenseness of the autochtonous muscles of the back, e.g. caused by static problems, or other functional disorders of the spine, can lead to back pain.

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