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Intrinsic back muscles - want to learn more about it?

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Intrinsic back muscles

The intrinsic back muscles are part of the trunk musculature. They comprise a system of well-developed,  deep muscles, which collectively extend along the length of the vertebral column. They are located in an osteofibrous canal, bounded by the vertebrae, ribs and thoracolumbar fascia. These muscles are most deeply located muscles of the back, and are differentiated from the extrinsic muscles by the fact that they actually develop in the back during embryogenesis.

The intrinsic muscles of the back are extremely important in maintaining posture and movements of the vertebral column

Key Facts
Medial tract Spinalis muscles
Transversospinalis muscles
Lateral tract Sacrospinal muscle
Intertransverse muscle
Spinotransverse muscle
Deep neck muscles Rectus capitis posterior major
Rectus capitis posterior minor
Obliquus capitis superior
Obliquus capitis inferior
Function Stabilization and movements of the vertebral column
Innervation Medial branches of the posterior rami of the spinal nerves

This article will describe all of the important anatomical facts about the intrinsic back muscles.

Overview

All intrinsic back muscles are innervated by the posterior rami of the spinal nerves.

Embryologically they derive from the dorsal part of the myotomes (epimere) which reside locally during the entire development for which reason they are also referred to as true or autochthonous back muscles.

In contrast, the extrinsic back muscles which are derived from the ventral part of the myotomes (hypomere), e.g. latissimus dorsi muscle and trapezius muscle, migrate into the trunk musculature subsequently (secondary back muscles).

The intrinsic back musculature is subdivided into a medial and lateral tract and the deep neck muscles.

Recommended video: Intrinsic muscles of the back: medial tract
Origins, insertions, innervation and functions of the medial tract of the intrinsic muscles of the back.

Medial tract

The medial tract extends between the spinal and transverse processes of the vertebrae. It is innervated by the medial branches of the posterior rami of the spinal nerves.

The medial tract can be further subdivided into the spinal, and transversospinal groups.

  • The spinalis muscles (spinalis thoracis, spinalis cervicis, and spinalis capitis) and the interspinales muscles belong to the spinal group of medial intrinsic muscles. They connect the spinal processes of neighboring vertebrae. The spinalis muscle originates slightly laterally from the interspinales muscles.
Key Facts about Spinalis and Interspinales muscles
Spinalis thoracis Origin - spinous processes of T10-L2
Insertion - spinous processes of T1-T8
Function - extension of the vertebral column and head
Spinalis cervicis Origin - lower portion of ligamentum nuchae, spinous process of C7
Insertion - spinous process of C2
Function - extension of the vertebral column and head
Spinalis capitis Origin - blends with semispinalis capitis
Insertion - with semispinalis capitis
Function - extension of the vertebral column and head
Interspinales  Origins and insertions - spinous processes of adjacent vertebrae
Function - stabilization of vertebral column during movements
Innervation Posterior branches of spinal nerves
  • The transversospinal groups comprises the thoracic and cervical rotatores muscles, multifidus muscle and the semispinalis muscles. They all run diagonally from the transverse to spinal processes. The short rotatores muscles insert at the next higher vertebrae, the long rotatores muscles at the second higher vertebrae. The multifidus muscle skips 2-4 vertebrae, the semispinalis muscle even 4-7 vertebrae. Furthermore the semispinalis muscle has a robust insertion at the occipital bone.
Key Facts about Transversospinal muscles
Semispinalis thoracis Origin - transverse processes T6-T10
Insertion - spinous processes of C6-T4
Semispinalis cervicis Origin - ransverse processes of T1-T5
Insertion - spinous processes of C2-C5
Semispinalis capitis Origin - transverse processes of C7-T6 and articular processes of C4-C6
Insertion - area between superior and inferior nuchal lines of occipital bone
Multifundus Origin - sacrum, posterior superior iliac spine, mammillary processes of lumbar vertebrae, transverse processes of thoracic vertebrae, articular processes of C4-C7
Insertion - base of spinous processes of C2-L5
Rotatores lumborum Origin - transverse processes of lumbar vertebrae
Insertion - spinous processes of lumbar vertebrae
Rotatores thoracis Origin - transverse processes of thoracic vertebrae
Insertion - spinous processes of thoracic vertebrae
Rotatores cervicis Origin - articular processes of cervical vertebrae
Insertion - spinous processes of cervical vertebrae
Innervation Posterior branches of spinal nerves
Function Bilateral contraction - extension of the spine (semispinalis capitis also extends the head)
Unilateral contraction - lateral flexion of the spine (semispinalis capitis also lateral flexes the head)

Lateral tract

The lateral tract is a collection of long longitudinal muscles. It lies more superficially than the medial tract and inserts more laterally. It is innervated by the lateral branches of the posterior rami of the spinal nerves. The lateral tract can be further subdivided into sacrospinal, intertransverse and spinotransverse muscular groups.

  • The sacrospinal group consists of the longissimus muscle and iliocostalis muscle. Both share an origin tendon at the thoracolumbar fascia. They have numerous origins and insertions at the ribs and transverse processes. In addition the longissimus capitis muscle inserts at the mastoid process of the temporal bone.
Key Facts about Iliocostalis and Longissimus muscles
Iliocostalis lumborum Origin - sacrum, spinous processes of T9-L5, iliac crest
Insertion - angles of the lower six ribs
Iliocostalis thoracis Origin - angles of lower six ribs
Insertion - angles of the upper six ribs
Iliocostalis cervicis Origin - angles of 3th to 6th ribs 
Insertion - transverse processes of C4-C6
Longissimus thoracis Origin - blends with iliocostalis in lumbar area, transverse processes of lumbar vertebrae
Insertion - transverse processes of T1-T12
Longissimus cervicis Origin - transverse processes of T1-T4
Insertion - transverse processes of C2-C6
Longissimus capitis Origin - transverse processes of T1-T5, articular processes of C4-C7
Insertion - posterior margin of mastoid process
Innervation Posterior branches of spinal nerves
Function Bilateral contraction - extension of the spine (semispinalis capitis also extends the head)
Unilateral contraction - lateral flexion of the spine (semispinalis capitis also lateral flexes the head)
  • The splenius muscles build the spinotransverse system. They originate at the spinal processes of the upper thoracic and cervical vertebrae and runs laterocranially.
  • The intertransverse group comprises the intertransversarii muscles and levatores costarum muscles. They extend between two neighboring transverse processes. The levatores costarum muscles are innervated by both the anterior and posterior branches of the spinal nerves (double innervation). Part of the intertransversarii muscles are even innervated only by anterior rami of the spinal nerves for which reason they do not count as intrinsic back muscles.
Key Facts about Splenius, Intertransversarii and Levatores costarum muscles
Splenius capitis Origin - lower half of ligamentum nuchae, spinous processes of C7-T4
Insertion - mastoid process, skull under the lateral third of superior nuchal line
Innervation - posterior rami of middle cervical nerves
Function - extension and rotation of the neck
Splenius cervicis Origin - spinous processes of T3-T6
Insertion - transverse processes of C1-C3
Innervation - posterior rami of lower cervical nerves
Function - extension of neck, rotation of head
Levatores costarum Origin - transverse processes of C7-T11
Insertion - te rib below vertebra of origin
Innervation - posterior rami of spinal nerves
Function - elevation of rib
Intertransversarii Origin and insertion - transverse processes of contiguous vertebrae
Innervation - posterior rami of spinal nerves
Function - stabilize vertebrae during movements of vertebral column
Recommended video: Intrinsic muscles of the back: lateral tract
Origins, insertions, innervation and functions of the lateral tract of the intrinsic muscles of the back.

Deep neck muscles

The deep neck muscles (suboccipital muscles) are innervated by the posterior branch of the first spinal nerve (C1), the suboccipital nerve, and are therefore considered as intrinsic back muscles. They consist of four paired muscles:

  • Rectus capitis posterior major muscle (spinal process of axisinferior nuchal line)
  • Rectus capitis posterior minor muscle (posterior tubercle of atlas → inferior nuchal line)
  • Obliquus capitis superior muscle (transverse process of atlas → inferior nuchal line)
  • Obliquus capitis inferior muscle (spinal process of axis → transverse process of atlas)
Key Facts about Deep neck muscles
Rectus capitis posterior major Origin - spinous process of C2
Insertion - lateral part of occipital bone below inferior nuchal line
Innervation - posterior branch of C1
Function - extension of head, rotation of head to the same side
Rectus capitis posterior minor Origin - posterior tubercle of C1
Insertion - medial part of occipital bone below inferior nuchal line
Innervation - posterior ramus of C1
Function - extension of head
Obliquus capitis superior Origin - transverse process of C1
Insertion - occipital bonebetween superior and inferior nuchal lines
Innervation - posterior ramus of C1
Function - extension and bending of head tothe same side
Obliquus capitis inferior Origin - spinous process of C2
Insertion - transverse process of C1
Innervation - posterior ramus of C1
Function - rotation of head to the same side

Function

The intrinsic back musculature is essential for the stabilization and movement of the vertebral column. Bilateral contraction stretches the body (dorsal extension), unilateral contraction bends the body to one side (lateral flexion). Rotation of the trunk is effected with the assistance of the oblique abdominal muscles.

The deep neck muscles support the movement of the atlanto-occipital joint. They have particularly many muscle spindles contributing to the proprioception of the head.

Intrinsic back muscles - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 931,206 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1.Auflage, Urban & Fischer Verlag/Elsevier (2008), S.136-140
  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.142-149
  • K. Zilles/B.Tillmann: Anatomie, 1.Auflage, Springer Medizin Verlag (2010), S.168-178

Author & Layout:

  • Achudhan Karunaharamoorthy
  • Christopher A. Becker

Illustrators:

  • First Illustration Gallery - Yousun Koh
  • Second Illustration Gallery - Rebecca Betts, Yousun Koh
  • Third Illustration Gallery - Yousun Koh
  • Fourth Illustration Gallery - Yousun Koh
  • Fifth Illustration Gallery - Paul Kim
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Related diagrams and images

Intrinsic muscles of the back

Superficial muscles of the back

Cervical spine

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