Erector Spinae Muscles

Erector Spinae Muscles

The Erector spinæ is a muscle group of the back in humans and animals. 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 vertebræ 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 vertebræ, 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:

Iliocostalis:

The iliocostalis originates from the sacrum, erector spinae aponeurosis and iliac crest. The iliocostalis has three different insertions according to the parts:

• iliocostalis lumborum has the lumbar part(where its insertion is in the 12th to 7th ribs)
• iliocostalis thoracis where its insertion runs from the last 6 ribs to the first 6 ribs.
• iliocostalis cervicis which runs from the first 6 ribs to the posterior tubercle of the transverse process of C6-C4.

Longissimus:

The longissimus muscle has three parts with different origin and insertion:

• longissimus thoracis originates from the sacrum,the spinous process of lumbar vertebrate and transverse process of the last thoracic vertebrate and inserts in the transverse process of the lumbar vertebrate,erector spinae aponeurosis,ribs and coastal process of thoracic vertebrate.
• longissimus cervicis originates from the transverse process of T6-T1 and inserts in the transverse process of C7-C2.
• longissimus capitis originates from the transverse process of T3-T1 runs through C7-C3 and inserts in the mastoid process of temporal bone.

Spinalis:

The spinalis muscle, as usual, has three parts:

• spinalis thoracis which originates from the spinous process of L3-T10 and inserts in the spinous process of T8-T2.
• spinalis cervicis originates from the spinous process of T2-C6 and inserts in the spinous process of C4-C2.
• spinalis capitis is an inconstant muscles fibres that runs from the cervical and upper thoracic which then inserts in the external occipital protuberance.

From lateral to medial, the erector spinae muscles can be remembered using the mnemonic, "I Long for Spinach" for Illiocostalis, Longissimus and Spinalis.