Intrinsic or Deep or Paraspinal Muslces of Back: Brief Outline

What are Paraspinal Muscles or Deep Muscles or Intrinsic Muscles of back?
These are deep or intrinsic back muscles. These muscles form a prominent mass on each side of the spinal column extending from base of the skull to the sacrum. These muscles consists of many separate, overlapping muscles of different lengths, attached to the spinous or transverse processes of different vertebrae. 

Together, these muscles act to maintain the posture and control the movements of vertebral column like backward bend.

The deep back muscles are grouped according to their relationship to the surface.

Superficial layer (of deep back muscles)

Splenius muscles

  • thick and flat muscles of the neck,
  • lie on the  side and on more aspect of neck,
  • arise from the midline and extend superolaterally to the cervical vertebra (slpenius cervicis) and skull (splenius capitis)

    Intermediate layer of deep back muscles

Erector spinae

  • Lies in a groove on each side of vertebral column
  • Chief extensor (backward bend) of vertebral column
  • Divides into three column

                                Iliocostalis – lateral column
                                Longissimus – intermediate column
                                Spinalis – medial column

Each column is divided regionally into three parts according to its superior attachments (e.g. iliocostalis lumborum, iliocostalis thoracis and iliocostalis cervicis; thoracis, cervicis and capitis in case of longissimus and spinalis)

Arises through a broad tendon from the posterior part of iliac crest, posterior aspect of sacrum and the sacroiliac ligaments, and sacral and inferior lumbar spinous processes

Deep layer of intrinsic back muscles
Transversosinal muscle group

  • Obliquely disposed deep to the erector spinae
  • Arises from transverse processes of vertebrae and pass to the spinous processes of more superior vertebrae
  • Three types 
               The semispinalis is superficial
               The multifidus is deeper
               The rotators are the deepest

Minor deep layer of intrinsic back muscles

Interspinales, intertransversarii and levatores costarum are poorly developed in the thoracic region
Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):

K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy