Erector spinae muscles

Erector spinae
The erector spinae muscle group
Details
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
Identifiers
Latin	Musculus erector spinae
Dorlands /Elsevier	m_22/12550616
TA	A04.3.02.002
FMA	71302
Anatomical terms of muscle

The erector spinae (/ˌɪˈrɛktər ˈspaɪni/ i-REK-tər SPY-nee)^[1] or spinal erectors is a set of muscles that straighten and rotate the back.

Structure

The erector spinae 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. 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:

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 is the intermediate and the largest of the three columns, it has three parts with different origin and insertion:

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

Spinalis

The spinalis muscle is the most medial and the smallest column. It 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 that then inserts in the external occipital protuberance.

From lateral to medial, the erector spinae muscles can be remembered using the mnemonic, I Love Spine. I lliocostalis, Love Longissimus and Spine Spinalis.^[2]

Training

Examples of exercises by which the erector spinae can be strengthened for therapeutic or athletic purposes include, but are not limited to:

• Bent-over row
• Deadlift
• Hyperextension
• Good-morning
• Pull-up (exercise)
• Rowing
• Squat
• Utkatasana
• Bridge (exercise)

Additional images

• 
  Right hip bone. Internal surface.
• 
  Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the lumbodorsal fascia.
• 
  The posterior divisions of the sacral nerves.
• 
  Transverse section, showing the relations of the capsule of the kidney.
• 
  Surface anatomy of the back.
• 
  Lumbar triangle

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

External links

• Anatomy figure: 01:05-03 at Human Anatomy Online, SUNY Downstate Medical Center - "Intermediate layer of the extrinsic muscles of the back, deep muscles."
• ithaca.edu