The erector spinae muscle group
|Origin||Spinous processes of T9-T12 thoracic vertebrae, medial slope of the dorsal segment of illiac crest|
|Insertion||spinous processes of T1 and T2 thoracic vertebrae and the cervical vertebrae|
|Artery||lateral sacral artery|
|Nerve||posterior branch of spinal nerve|
|Actions||extends the vertebral column|
|Antagonist||rectus abdominis muscle|
|Latin||Musculus erector spinae|
|Anatomical terms of muscle|
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The erector spinae is not just one muscle, but a bundle of muscles and tendons which run more or less vertically and are paired left to right. These muscles lie in the groove to the side of the vertebral column and extend throughout the lumbar, thoracic, and cervical regions. The erector spinae is covered in the lumbar and thoracic regions by the thoracolumbar fascia, and in the cervical region by the nuchal ligament.
This large muscular and tendinous mass varies in size and structure at different parts of the vertebral column. In the sacral region, it is narrow and pointed, and at its origin chiefly tendinous in structure. In the lumbar region, it is larger, and forms a thick fleshy mass. Further up, it is subdivided into three columns. They gradually diminish in size as they ascend to be inserted into the vertebrae and ribs.
The erector spinae arises from the anterior surface of a broad and thick tendon. It is attached to the medial crest of the sacrum, to the spinous processes of the lumbar and the eleventh and twelfth thoracic vertebrae and the supraspinous ligament, to the back part of the inner lip of the iliac crests, and to the lateral crests of the sacrum, where it blends with the sacrotuberous and posterior sacroiliac ligaments.
Some of its fibers are continuous with the fibers of origin of the gluteus maximus.
The muscular fibers form a large fleshy mass that splits, in the upper lumbar region, into three columns, viz., a lateral (iliocostalis), an intermediate (longissimus), and a medial (spinalis). Each of these consists of three parts, inferior to superior, as follows:
The longissimus muscle is the intermediate and the largest of the three columns. It has three parts with different origin and insertion:
The spinalis muscle is the smallest and most medial column. It has three parts:
|Lower thoracic vertebrae and ribs||I. lumborum|
|Upper thoracic vertebrae and ribs||I. thoracis||L. thoracis||S. thoracis|
|Cervical vertebrae||I. cervicis||L. cervicis||S. cervicis|
|Skull||L. capitis||S. capitis|
Examples of exercises by which the erector spinae can be strengthened for therapeutic or athletic purposes include, but are not limited to: