UNIT 1 - Second Order Info

Latissimus dorsi — Superficial layer of extrinsic back

O: Spinous processes of T7-L5, thoracolumbar fascia, iliac crest, ribs 9-12, and the inferior angle of the scapula

Insertion: Intertubercular sulcus of humerus

A: Extends, adducts, and medially rotates the arms; assists in respiration

Innervation: Thoracodorsal nerve

Levator scapulae— Superficial layer of extrinsic back

• O: Transverse processes of C1-C4

• Insertion: Superior part of medial border of scapula

• A: Elevates and inferiorly rotates the scapula (rotating the glenoid cavity inferiorly)

  • When contracting bilaterally, it extends the neck

  • When contracting unilaterally, it produces lateral flexion of the neck

• Innervation: Dorsal scapular nerve

Rhomboid major— Superficial layer of extrinsic back

• O: Spinous processes of T2-T5

• Insertion: Medial border of scapula from spine to inferior angle

• A: Retracts and elevates the scapula, inferiorly rotates the scapula, and stabilizes the scapula against the thoracic wall

• Innervation: Dorsal scapular nerve

Rhomboid minor— Superficial layer of extrinsic back

• O: Nuchal ligament and spinous processes of C7-T1

• Insertion: Medial border of scapula at root of spine

• A: Retracts and elevates scapula, inferiorly rotates the scapula, and stabilizes the scapula against the thoracic wall

• Innervation: Dorsal scapular nerve

Serratus posterior inferior—Intermediate layer of extrinsic back

O: Spinous processes of T11-L2

Insertion: Inferior of ribs 9-12

A: Depresses ribs during exhalation, contributing to forced expiration

Innervation: Anterior rami of T9-T12 spinal nerves

Serratus posterior superior— Intermediate layer of extrinsic back

O: Nuchal ligament, spinous processes of C7-T3

Insertion: Superior borders of ribs 2-5

A: Elevates ribs during inhalation, particularly during forced respiratory effort

Innervation: Anterior rami of T2-T5 spinal nerves

Trapezius—Superficial layer of extrinsic back

O: External occipital protuberance (of occipital bone), superior nuchal line (or occipital bone), nuchal ligament, and spinous processes and supraspinous ligaments of C7-T12

Insertion: Lateral third of clavicle, acromion, spine of scapula

A: Elevates, retracts, depresses, and superiorly rotates scapula

Innervation: Spinal accessory nerve (CN XI); C3-C4 spinal nerve (sensory)

Spinalis cervicis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Spinous processes of upper cervical vertebrae

A: Extends vertebral column

Innervation: Posterior (dorsal) rami of cervical and thoracic spinal nerves

Spinalis thoracis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Spinous processes of upper thoracic vertebrae

A: Extends vertebral column

Innervation: Posterior (dorsal) rami of cervical and thoracic spinal nerves

Longissimus capitis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Mastoid process of temporal bone

A: Bilateral contraction: extends head

• Unilateral contraction: ipsilaterally rotates head

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerve

Longissimus cervicis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Transverse processes of cervical vertebrae

A: Bilateral contraction: extension and stabilization of vertebral column

• Unilateral contraction: lateral flexion of vertebral column

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerve

Longissimus thoracis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Transverse processes of cervical vertebrae and ribs

A: Bilateral contraction: extension and stabilization of vertebral column

• Unilateral contraction: lateral flexion of vertebral column

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerve

Iliocostalis cervicis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Angles of lower ribs, transverse processes of cervical vertebrae

A: Unilateral contraction: lateral flexion of vertebral column

• Bilateral contraction: extension and stabilization of vertebral column

Innervation: Posterior (or dorsal) rami of cervical, thoracic, and lumbar spinal nerve

Iliocostalis thoracis—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Angles of lower ribs, transverse processes of cervical vertebrae

A: Unilateral contraction: lateral flexion of vertebral column

• Bilateral contraction: extension and stabilization of vertebral column

Innervation: Posterior (or dorsal) rami of cervical, thoracic, and lumbar spinal nerve

Iliocostalis lumborum—Intermediate layer of intrinsic (true) back

• Erector spinae muscles

O: different origins, erector spinae muscle as a group: posterior/medial part of iliac crest, posterior surface of sacrum, median sacral crest, sacro-ligaments, spinous processes of lower lumbar vertebrae, supraspinous ligament

Insertion: Angles of lower ribs, transverse processes of cervical vertebrae

A: Unilateral contraction: lateral flexion of vertebral column

• Bilateral contraction: extension and stabilization of vertebral column

Innervation: Posterior (or dorsal) rami of cervical, thoracic, and lumbar spinal nerve

Semispinalis capitis—Major deep layer of intrinsic (true) back

• Transversospinalis muscles

O: Articular process of cervicial vertebrae and transverse process of cervicial and thoracic vertebrae

Insertion: Between superior and inferior nuchal lines of occipital bone

A: Unilateral contraction: contralateral rotation of head (or neck) and vertebral column (or torso)

• Bilateral contraction: extends head (or neck) and extends vertebral column (or torso)

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerves

Semispinalis cervicis—Major deep layer of intrinsic (true) back

• Transversospinalis muscles

O: Transverse processes of upper thoracic vertebrae

Insertion: Spinous process of C2-C5

A: Unilateral contraction: contralateral rotation of head (or neck) and vertebral column (or torso)

• Bilateral contraction: extends head (or neck) and extends vertebral column (or torso)

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerves

Semispinalis thoracis—Major deep layer of intrinsic (true) back

• Transversospinalis muscles

O: Transverse processes of lower thoracic vertebrae

Insertion: Spinous process of lower cervical and upper thoracic vertebrae

A: Unilateral contraction: contralateral rotation of head (or neck) and vertebral column (or torso)

• Bilateral contraction: extends head (or neck) and extends vertebral column (or torso)

Innervation: Posterior (or dorsal) rami of cervical and thoracic spinal nerves

Splenius capitis—Superficial layer of intrinsic (true) back

O: Nuchal ligament and spinous processes of C7-T3

Insertion: Mastoid process of temporal bone and lateral third of superior nuchal line of occipital bone

A: Unilateral contraction: lateral flexion and rotation of the head to the same side (ipsilateral movement)

• Bilateral contraction: extension of the head

Innervation: Posterior (or dorsal) rami of middle cervical spinal nerves

Splenius cervicis—Superficial layer of intrinsic (true) back

O: Spinous processes of T3-T6

Insertion: Transverse processes of C1-C3

A: Unilateral contraction: lateral flexion and rotation of the cervical spine to the same side (ipsilateral movement)

• Bilateral contraction: extension of cervical spine

Innervation: Posterior (or dorsal) rami of middle cervical spinal nerves

Multifidus—Major deep layer intrinsic (true) back

• Transversospinalis muscles

O: Posterior sacrum, posterior superior iliac spine of ilium, common origin tendon of erector spinae, sacro-iliac ligaments, mamillary processes of lumbar vertebrae, transverse processes of upper thoracic vertebrae, articular processes of lower half of cervical vertebrae

Insertion: Spinous processes 2-4 vertebrae superior to origin

A: Stabilize vertebrae during local movements of vertebral column

Innervation: Posterior (or dorsal) rami of cervical, thoracic, and lumbar spinal nerves

Rotatores brevis/longus—Major deep layer intrinsic (true) back

• Transversospinalis muscles

O: Transverse processes of vertebrae (most developed in thoracic region)

Insertion: Junction of lamina and spinous process of vertebra one (brevis) or two (longus (levels) above the origin

A: Stabilizes the vertebrae and assists with local extension and rotatory movements of the vertebral column; may have some proprioceptive function

Innervation: Posterior (or dorsal) rami of cervical, thoracic, and lumbar spinal nerves

Levatores costarum—Minor deep layer of intrinsic (true) back

• Erector spinae muscles

O: Transverse processes of C7-T11

Insertion: Ribs inferior to origin, between tubercle and angle ribs

A: Elevates ribs, assisting in respiration; assists with lateral flexion of vertebral column

Innervation: Posterior (or dorsal) rami of spinal nerves

Intertransversarii—Minor deep layer of intrinsic (true) back

O & Insertion: Between transverse processes of adjacent cervical and lumbar vertebrae

A: Unilateral contraction: Aids in lateral flexion of vertebral column

• Bilateral contraction: Stabilizes vertebral column

Innervation: Posterior (dorsal) rami of spinal nerves

Interspinales—Minor deep layer of intrinsic (true) back

O & Insertion: Spinous processes of cervical and lumbar vertebrae

A: Aids in extorsion and rotation of vertebral column

Innervation: Posterior (dorsal) rami of spinal nerves

Obliquus capitis inferior—Suboccipital region

O: Spinous processes of C2/axis

Insertion: Transverse process of C1

A: Rotates head to same side of contraction (ipsilateral rotation)

Innervation: Suboccipital nerve (posterior ramus of C1)

Obliquus capitis superior—Suboccipital region

O: Transverse process of C1/atlas

Insertion: Occipital bone between superior and inferior nuchal lines

A: Bilateral contraction: Extends head

• Unilateral contraction: Laterally flexes head

Innervation: Suboccipital nerve (posterior ramus of C1)

Rectus capitis posterior major—Suboccipital region

O: Spinous process of C2/axis

Insertion: Inferior nuchal line of occipital bone

A: Bilateral contraction: extends head

• Unilateral contraction: Rotates head to the same side of contraction (ipsilateral rotation)

Innervation: Suboccipital nerve (posterior ramus of C1)

Rectus capitis posterior minor—Suboccipital region

O: Posterior tubercle of C1/atlas

Insertion: Medial part of inferior nuchal line of occipital bone

A: Extends head

Innervation: Suboccipital nerve (posterior ramus of C1)