ANATOMY-SPINE-MUSCLES


MUSCLES of the SPINAL COLUMN 


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ERECTOR SPINAE GROUP


Last revised by Assoc Prof Craig Hacking on 02 Aug 2021

The erector spinae group is the intermediate layer of the intrinsic muscles of the back. This group is made of 3 subgroups, with the group divisions occurring by location.

  1. iliocostalis subgroup is the most lateral
  2. longissimus subgroup is between iliocostalis and spinalis
  3. spinalis subgroup is the most medial

INNERVATION


  • lateral branches of dorsal rami of cervical, thoracic and lumbar spinal nerves
  • at the lumbar levels, lateral branches of the dorsal rami innervate iliocostalis and intermediate branches innervate longissimus

FUNCTION


  • extensors of the back when the thoracic and lumbar components of the erector spinae act bilaterally
  • lateral flexion when the thoracic and lumbar components act unilaterally
  • control of the descent of the thorax towards gravity when the abdominal muscles contract until abdominal muscles are fully flexed – at that point flexion is limited by passive tension from the components of the back.
  • control of the descent of the thorax towards gravity during lateral flexion, aided by the abdominal obliques
  • functions of the cervical and capital erector spinae muscles are not clear

TRANSVERSOSPINALIS MUSCLE GROUP


Last revised by Assoc Prof Craig Hacking on 02 Aug 2021

The Transversospinalis muscle group is the deep layer of the intrinsic back muscles. These muscles lie between the transverse and spinous processes and are grouped by length of the fascicles, as well as region covered. The groups are:

  1. Rotatores
  2. Multifidus
  3. Semispinalis

INNERVATION


  • Rotatores, Multifidus, Semispinalis Thoracis and Cervicis muscles: medial branches of dorsal rami of associated spinal nerves
  • Semispinalis Capitis muscle: descending branch of the greater occipital nerve (C2) and the C3 spinal nerve

FUNCTION


  • all of the Transversospinalis muscles are extensors of the back and neck
  • Rotatores muscles are identified as rotators in many texts, but this action has not been validated and the Rotatores are more likely stabilizers of the spinal column
  • the Multifidus and Semispinalis muscle group has also been identified as rotators by some texts and refuted in others

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