BACK MUSCLES

• What back muscles are superficial?

  • Associated with movements of the shoulder.
  • Extrinsic muscles because they do not develop in the back.
  • Including: Trapezius, Latissimus Dorsi, Levator Scapulae, Rhomboids.

  
• Trapezius:

  • Broad, flat and triangular muscle.
  • The most superficial of all the back muscles.
  • O: skull, ligamentum nuchae and SP C7-T12
  • I: clavicle, acromion, and spine of scapula
  • A:
  • N: Accessory nerve and spinal nerve (C3,4)

  
• Latissimus Dorsi

  • O: SP T6-T12, thoracolumbar fascia, iliac crest, and inferior three ribs.
  • I: Intertubercular sulcus of the humerus
  • A: Extend, adduct and internally rotate the upper limb.
  • N: Thoracodorsal nerve

  
• Levator Scapulae

  • A small strap- like muscle
  • O: TVP of C1- C4
  • I: medial border of the scapula
  • A: Elevate the scapula
  • N: Dorsal scapular nerve

  
• Rhomboid Major:

  • O: SP T2- T5
  • I: medial border of scapula (b/w scapula spine and inferior angle)
  • A: Retract and rotate the scapula
  • N: Dorsal scapular nerve

  
• Rhomboid Minor:

  • O: SP of C7- T1
  • I: medial border of scapula (at the level of the spine of scapula)
  • A: Retract and rotate the scapula
  • N: Dorsal scapular nerve

  
• What back muscles are in the intermediate group?

  • Associated with movements of the thoracic cage.
  • Extrinsic muscle because they do not develop in the back.
  • Containing 2 muscles: Serratus Posterior Superior and Serratus Posterior Inferior

  
• Serratus Posterior Superior:

  • Thin, rectangular shaped muscle, deep to the rhomboids muscle.
  • O: lower part of the ligamentum nuchae, SP C7- T3
  • I: Ribs 2-5 (pass in an inferolateral direction.
  • A: Elevate ribs 2-5
  • N: Intercostal nerves

  
• Serratus Posterior Inferior:

  • Broad and strong, lies underneath the Latissimus Dorsi.
  • O: SP T11- L3
  • I: ribs 9-12 (pass in a superolateral direction)
  • A: Depress ribs 9-12
  • N: Intercostal nerves

  
• What back muscles are intrinsic back muscles?

  • Associated with movements of the vertebral column.
  • Develop embryologically in the back.
  • Divided into 3 layers: superficial (spinotransversales- splenius capitis and cervicis), intermediate (erector spinae), deep (transversospinales)
• Splenius Capitis:

  • Superficial muscles of deep group
  • Located on the posterolateral aspect of the neck, covering the deeper neck muscles.
  • O: lower aspect of the ligamentum nuchae, SP C7- T3/4
  • I: mastoid process and the occipital bone of the skull
  • A: Rotate head to the same side
  • N: Posterior rami of spinal nerve C3, 4

  
• Splenius Cervicis

  • O: SP of T3- T6
  • I: TVP of C1- 3/4
  • A: Rotate the head to the same side
  • N: Posterior rami of the lower cervical spinal nerves.

  
• Iliocostalis:

  • intermediate intrinsic back muscles
  • Form a column, known as erector spinae.
  • Situated posterolaterally to spinal column, b/w the vertebral SP