Regions and Muscles of the Back

• Functions of back muscles:

  • Support the body's weight, transmission of forces through pelvis to lower limbs, carry and position the head, brace and help manoeuvre the upper limbs
  • Movement
• Classification of muscles:

  • Extrinsic muscles: do not develop embryologically from the back (superficial and intermediate groups)
  • Superficial muscles: movement of upper limbs
  • Intermediate muscles: movement of thoracic cage
  • Intrinsic muscles: developed embryologically from the back (deep group) for movements of vertebral column
• Superficial back muscles:

  • Immediately deep to skin and superficial fascia
  • Attach superior part of appendicular skeleton to axial skeleton
  • Responsible for movements of the scapulae and shoulders
  • Arranged in two layers:
  • Superficial layer:
  • m. trapezius
  • m. latissimus dorsi
  • Deep layer:
  • mm. rhomboidei
  • m. levator scapulae
• Trapezius:

  • Attachments:
  • Origin: external occipital protuberance, ligamentum nuchae, spinous processes C7 - T12
  • Insertion: lateral third of clavicle, acromion and scapula spine
  • Innervation:
  • Motor: accessory nerve
  • Proprioception: C3 and C4 spinal nerves
  • Function: elevation and rotation of scapula during abduction of humerus, retraction of scapula
• Latissimus dorsi:

  • Attachments:
  • Origin: spinous processes T7 - L5, iliac crest, thoracolumbar fascia and inferior 3 ribs
  • Insertion: intertubercular sulcus
  • Innervation: thoracodorsal nerve
  • Function: extension, adduction, medial rotation of humerus
• Levator scapulae:

  • Attachments:
  • Origin: transverse processes C1 - C4
  • Insertion: Medial border of scapula
  • Innervation: C3 to C4 and dorsal scapular nerve
  • Function: elevation of scapula
• Rhomboid major and minor:

  • Rhomboid major:
  • Attachments:
  • Origin: spinous processes T2 - T5
  • Insertion: medial border of scapula (between spine and inferior angle)
  • Rhomboid minor:
  • Attachments:
  • Origin: spinous processes of C7 and T1
  • Insertion: medial border of scapula (at spine of scapula)
  • Innervation: Dorsal scapular nerve
  • Function: retraction and elevation of scapula
• Intermediate muscles of the back:

  • Serratus posterior superior:
  • Attachments:
  • Origin: lower part of ligamentum nuchae, spinous processes C7 - T3
  • Insertion: upper border of ribs 2 - 5
  • Innervation: anterior rami T2 - T5
  • Function: elevation of ribs 2 to 5
  • Serratus posterior inferior:
  • Attachments:
  • Origin: spinous processes T11 - L3
  • Insertion: lower border of ribs 9 - 12
  • Innervation: anterior rami T9 to T12
  • Function: Depression of ribs 9 - 12
• Erector spinae muscles:

  • Made up of 3 columns of muscles: Iliocostalis, Longissimus, Spinalis
  • Functions: extension of vertebral column and head, flexion of vertebral column, act bilaterally to straighten the head
  • Innervation: posterior rami of spinal nerves
• Transversospinales muscles:

  • 3 major muscles in this group: Semispinalis (capitis, cervicis, thoracis), Multifidus, Rotatores (cervicis, thoracis, lumborum)
  • Functions: extend the vertebral column, rotation of trunk to one side
  • Innervation: posterior rami of spinal nerves
• Segmental muscles:

  • Levatores costarum elevate ribs
  • Interspinales and intertransversarii stabilize vertebral column during movements
  • Innervation: posterior rami of spinal nerves
• Fasciae of the back:

  • Deep fascia of the cervico-dorsal region, fascia nuchae
  • Thoracolumbar fascia, fascia thoracolumbalis:
  • Between the superficial and deep back muscles
  • Composed of two layers: superficial (posterior) layer along the whole back region, deep (anterior) layer in the lumbar region
• Nerves of the nuchal region:

  • Motor and sensory innervation from the posterior rami of the spinal nerves
  • Specific names for posterior rami of C1 – C3: suboccipital nerve (C1), greater occipital nerve (C2), third occipital nerve (C3)
  • Lesser occipital and great auricular nerves arise from the anterior rami of the C1 – C4 spinal nerves and innervate the skin of the anterolateral head and neck
  • Anterior rami of C1 – C4 give rise to the ansa cervicalis, which innervates the infrahyoid muscles
• The muscles of the back can be divided into three groups: superficial, intermediate, and intrinsic
• Superficial muscles are associated with movements of the shoulder
• Intermediate muscles are associated with movements of the thoracic cage
• Deep muscles are associated with movements of the vertebral column and develop embryologically in the back
• The deep muscles of the back collectively extend from the sacrum to the base of the skull and are covered by deep fascia
• The deep back muscles can be divided into three layers: superficial, intermediate, and deep
• Superficial muscles, also known as the spinotransversales, include splenius capitis and splenius cervicis
• Splenius Capitis:

  • Originates from the lower aspect of the ligamentum nuchae and the spinous processes of C7 – T3/4 vertebrae
  • Attaches to the mastoid process and the occipital bone of the skull
  • Innervated by posterior rami of spinal nerves C3 and C4
  • Rotates head to the same side
• Splenius Cervicis:

  • Originates from the spinous processes of T3 – T6 vertebrae
  • Attaches to the transverse processes of C1-3/4
  • Innervated by posterior rami of the lower cervical spinal nerves
  • Rotates head to the same side
• Intermediate intrinsic back muscles include iliocostalis, longissimus, and spinalis, forming the erector spinae
• Iliocostalis:

  • Arises from the common tendinous origin and attaches to the costal angle of the ribs and the cervical transverse processes
  • Innervated by posterior rami of the spinal nerves
  • Acts unilaterally to laterally flex the vertebral column and bilaterally to extend the vertebral column and head
• Longissimus:

  • Arises from the common tendinous origin and attaches to the lower ribs, the transverse processes of C2 – T12, and the mastoid process of the skull
  • Innervated by posterior rami of the spinal nerves
• Splenius Capitis:

  • Originates from the lower aspect of the ligamentum nuchae, and the spinous processes of C7 - T3/4 vertebrae
  • Fibres attach to the mastoid process and the occipital bone of the skull
  • Innervated by posterior rami of spinal nerves C3 and C4
  • Rotates head to the same side
• Splenius Cervicis:

  • Originates from the spinous processes of T3 – T6 vertebrae
  • Fibres attach to the transverse processes of C1-3/4
  • Innervated by posterior rami of the lower cervical spinal nerves
  • Rotates head to the same side
• Iliocostalis:

  • Arises from the common tendinous origin
  • Attaches to the costal angle of the ribs and the cervical transverse processes
  • Acts unilaterally to laterally flex the vertebral column
  • Acts bilaterally to extend the vertebral column and head
• Semispinalis:

  • Originates from the transverse processes of C4-T10
  • Fibres ascend 4-6 vertebral segments, attaching to the spinous processes of C2-T4, and to the occipital bone of the skull
  • Innervated by posterior rami of the spinal nerves
  • Extends and contralaterally rotates the head and vertebral column
• Multifidus:

  • Has a broad origin - arises from the sacrum, posterior iliac spine, common tendinous origin of the erector spinae, mamillary processes of lumbar vertebrae, transverse processes of T1-T3 and articular processes of C4-C7
  • Fibres ascend 2-4 vertebral segments, attaching to the vertebral spinous processes
  • Innervated by posterior rami of the spinal nerves
  • Stabilises the vertebral column
• Rotatores:

  • Originates from the vertebral transverse processes
  • Fibres ascend and attach to the lamina and spinous processes of the vertebrae above
  • Contributes to extension and rotation of the vertebral column
  • Stabilises the vertebrae and has a proprioceptive function
  • Innervated by posterior rami of the spinal nerves
• Interspinales:

  • Spans between adjacent spinous processes
  • Acts to stabilise the vertebral column
• Intertranversarii:

  • Spans between adjacent transverse processes
  • Acts to stabilise the vertebral column
• Longissimus:

  • Arises from the common tendinous origin
  • Attaches to the lower ribs, the transverse processes of C2 - T12, and the mastoid process of the skull
  • Acts unilaterally to laterally flex the vertebral column
  • Acts bilaterally to extend the vertebral column and head
• Levatores costarum:

  • Originates from the transverse processes of C7-T11
  • Attaches to the rib immediately below
  • Acts to elevate the ribs
• Superficial muscles and elements

  • Back