The Erector spinę is a muscle group of the back in humans and animals, which extends the vertebral column (bending the spine such that the head moves posteriorly while the chest protrudes anteriorly). It is also known as sacrospinalis in older texts. A more modern term is extensor spinae, though this is not in widespread use. The name of the muscle is pronounced e-rec-tor speen-aye, or e-rec-tor spinae-ee.
It is not just one muscle, but a bundle of muscles and tendons. It is paired and runs more or less vertically. It extends throughout the lumbar, thoracic and cervical regions, and lies in the groove to the side of the vertebral column.
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 which, on being followed upward, is subdivided into three columns; these gradually diminish in size as they ascend to be inserted into the vertebrę and ribs.
The erector spinae arises from the anterior surface of a broad and thick tendon, which is attached to the medial crest of the sacrum, to the spinous processes of the lumbar and the eleventh and twelfth thoracic vertebrę, 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 which splits, in the upper lumbar region into three columns, viz., a lateral, the Iliocostalis, an intermediate, the Longissimus, and a medial, the Spinalis. Each of these consists of three parts, inferior to superior, as follows:
The iliocostalis originates from the sacrum, erector spinae aponeurosis and iliac crest. The iliocostalis has three different insertions according to the parts:
The longissimus muscle has three parts with different origin and insertion:
The spinalis muscle, as usual, has three parts:
From lateral to medial, the erector spinae muscles can be remembered using the mnemonic, "I Long for Spinach" for Illiocostalis, Longissimus and Spinalis.
Examples of exercises by which the erector spinae can be strengthened for therapeutic or athletic purposes include, but are not limited to:
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