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Erector spinae muscles

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Title: Erector spinae muscles  
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Erector spinae muscles

Erector spinæ
The erector spinae muscle group
Details
Latin Musculus erector spinae
Origin Spinous processes of T9-T12 thoracic vertebræ, medial slope of the dorsal segment of illiac crest
Insertion spinous processes of T1 and T2 thoracic vertebrae and the cervical vertebrae
lateral sacral artery
posterior branch of spinal nerve
Actions extends the vertebral column
Antagonist rectus abdominis muscle
Dorlands
/Elsevier
m_22/12550616
Anatomical terms of muscle

The erector spinæ ( )[1] is a muscle group of the back in humans and other 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,[2] though this is not in widespread use.

Contents

  • Structure 1
    • Iliocostalis 1.1
    • Longissimus 1.2
    • Spinalis 1.3
  • Function 2
  • Clinical significance 3
    • Training 3.1
  • Additional images 4
  • References 5
  • External links 6

Structure

The erector spinæ 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 spinæ 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. These gradually diminish in size as they ascend to be inserted into the vertebræ and ribs.

The erector spinæ 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 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 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:

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.
Insertion Lateral Column
Iliocostalis
Intermediate Column
Longissimus
Medial Column
Spinalis
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

From lateral to medial, the erector spinæ muscles can be remembered using the mnemonic, I Love Spinach. I lliocostalis, Love Longissimus and Spiniach Spinalis.[3]

Function

The erector spinae functions to straighten the back and provides for side-to-side rotation.

Clinical significance


Training

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

Additional images

References

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

  1. ^ "MedLine Plus - Erector spinae". Merriam Webster. Retrieved 16 April 2014.  Lat. "that which straightens out the spines"
  2. ^ Terminologia Anatomica, 1999.
  3. ^ "Medical mnemonic". LifeHugger. Retrieved 2009-12-15. 

External links

  • -596967347 at GPnotebook
  • 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
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