Summary

• Superficial and deep muscles of the back

  • Superficial muscles
  • Deep muscles
• Superficial muscles of the back


  • Muscles of the back related to the upper limb
  • Muscles of the thorax
• Trapezius muscle


  • Flat and broad muscle occupying superficial portion at the back of the neck and upper part of the back
  • Triangular with the base facing the vertebral column and the apex directed to the region of the scapula
  • Muscles of both sides meet to form a diamond shape
• Trapezius muscle action


  1. Draws the scapula to the vertebral column

  2. Contraction of upper fibers raises the scapula

  3. Contraction of lower fibers lowers the scapula

  4. When the scapula is fixed, both superior and inferior fibers pull the head backwards

  5. Contraction of one muscle tilts the head to the corresponding side
• Latissimus dorsi muscle


  Large muscle located specially in the lower part of the back
• Latissimus dorsi muscle action


  1. Draws the arm to the trunk and pulls the upper body backwards to the midline and at the same time rotates it medially (pronation)

  2. When the arm is fixed, the muscle pulls the trunk upwards on the arm or contributes to upward displacement of the lower ribs in respiratory excursions and is thus an accessory muscle of respiration
• Rhomboid major and minor muscles

  • Rhomboid-shaped muscles located under the trapezius
  • Rhomboid major arises from the spinous processes of the upper four thoracic vertebrae
  • Rhomboid minor arises from the spinous processes of the lower two cervical and upper two thoracic vertebrae
• Rhomboid muscles action


  Draw the scapula closer to the vertebral column along an oblique line directed to the midline and upwards
• Levator scapulae muscle


  • Originates as four separate slips from the posterior tubercles of the transverse processes of the upper four cervical vertebrae
  • Descends and slightly laterally to be inserted into the upper part of the medial border of the scapula and in part into the superior angle
• Levator scapulae muscle action

  1. Raises the scapula, its upper angle in particular, causing retraction as a whole of which the lower angle is displaced downwards towards the vertebral column

  2. When the scapula is fixed, the cervical part of the vertebral column is inclined backwards and to the side
• Serratus posterior superior muscle

  • Thin and covered by the rhomboid muscles
  • Arises on the superficial layer of the back fascia at the level of the lower two thoracic and upper three lumbar vertebrae
• Serratus posterior superior muscle action

  Elevates the upper ribs and thus takes part in the act of inspiration
• Serratus posterior inferior muscle

  • Thin and located under the latissimus dorsi muscle
  • Arises from the superficial layer of the back fascia at the level of the lower two thoracic and upper three lumbar vertebrae
• Serratus posterior inferior muscle action

  Depresses the lower ribs and thus takes part in the act of expiration
• Deep (proper) muscles of the back

  • Long muscles
  • Short muscles
• Splenius capitis muscle


  • Arises from the ligamentum nuchae and the spinous processes of the lower five cervical and upper three thoracic vertebrae
  • Inserted into the lateral parts of the superior nuchal line and the posterior border of the mastoid process
• Splenius cervicis muscle


  • Arises from the spinous processes of the lower five cervical and upper two thoracic vertebrae
  • Inserted into the posterior tubercles of the transverse processes of the upper two or three cervical vertebrae
• Splenius capitis and cervicis muscles action

  1. Bilateral contraction pulls the head and neck backwards

  2. Unilateral contraction rotates the head and neck to the side of the acting muscle
• Iliocostalis muscle


  • Divided into three parts: lumborum, thoracis, and cervicis
• Longissimus muscle


  • Strongest and longest muscle of the back
  • Completely fills the depression in the back formed to the sides of the spinous processes and extending to the angles of the ribs
  • Divided into three parts: iliocostalis, spinalis, and longissimus
• The deep muscles of the back are classified as long and short muscles
• The spinals de la mat pina (erector spinae) is the strongest and longest muscle of the back
• Erector spinae muscle


  • Completely fills the depression in the back formed to the sides of the spinous processes and extending to the angles of the ribs
  • Takes origin from the posterior part of the iliac crest, the dorsal surface of the sacrum, the spinous processes of the lower lumbar vertebrae, and partly from the superficial layer of the lumbar fascia
  • Ascends in the lumbar region into the following three parts: (1) the laterally located iliocostalis muscle; (2) the medially situated spinalis muscle; and (3) the longissimus muscle located between them
• Costocervicalis muscle


  • Takes origin from the angles of the upper five or seven ribs, also ascends obliquely and laterally, and is inserted by three slips into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae
• Longissimus muscle


  • Medial of the costocervicalis muscle and stretches from the sacrum to the base of the skull
  • Includes the following three parts: (a) the longissimus thoracis muscle, (b) the longissimus cervicis muscle, and (c) the longissimus capitis muscle
• Spinalis muscle


  • Lodged between the transverse processes of the upper four or three lumbar and lower two or three thoracic vertebrae
  • Includes the following three parts: (a) the spinalis thoracis muscle, (b) the spinalis cervicis muscle, and (c) the spinalis capitis muscle
• Transversospinalis muscle


  Relatively short muscles that run obliquely from the transverse processes of one vertebra to the spinous process of the contiguous vertebra above
• Rotator muscles


  • The deepest part of the transversospinalis muscle
  • Include the following parts: (a) the cervical rotators, (b) the thoracic rotators, and (c) the lumbar rotators
• The whole erector spinae muscle acts as a strong contractor of the vertebral column, and by bilateral contraction it extends the vertebral column
• Unilateral contraction of the erector spinae muscle bends the vertebral column to the same side
• The upper fibres (the splenius muscle) pull the head downwards
• The action of all parts of the erector spinae muscle is to extend the vertebral column and pull the head back or hold it in this position
• Fascia of the back

  • The superficial fascia of the back is a thin connective tissue layer that is part of the general superficial fascia covering the posterior wall of the back
  • The thoracolumbar fascia consists of two layers: a superficial layer and a deep layer
  • The superficial layer is attached below to the angles of the ribs and medially to the spinous processes of all the vertebrae except the cervical vertebrae
  • The deep layer extends between the transverse processes of the lumbar vertebrae, the iliac crest, and the twelfth rib
  • The transversus abdominis muscle takes origin from the deep layer and from its junction with the superficial layer