Download Back Muscles (Continued)

Back and Posterior Neck
Muscles
PTH 505
(c) Donald Allen
Overview of Back Muscles
• 3 Groups of muscles
– Superficial group
– Intermediate group
• The superficial and intermediate back muscles are
the extrinsic muscles of the back
• Both groups supplied by anterior rami
– Intrinsic group (deep, native)
• Primarily posterior rami
Superficial Back Muscles
• Act on upper extremity
• Anchor upper extremity to the axial
skeleton (from head and trunk to pelvic
girdle)
• Trapezius muscle
• Latissimus dorsi muscle
– Review the origin, insertion, innervation and
function of these muscles
Trapezius
muscle
Insert:
Yellow
• Muscle Action (head and trunk stable)
– Whole muscle
– Upper fibers
– Middle fibers
– Lower fibers
• Muscle Action (Shoulder girdle stable)
– Bilateral contraction
– Unilateral contraction
Latissimus
dorsi
muscle
16
• Origin
• Insertion
Intermediate Back Muscles
• Function in respiration
• Serratus posterior superior muscle
• Serratus inferior superior muscle
• These muscles may be more important in
proprioception rather than movement
• Cards: 122, 123
Serratus Posterior Superior Muscle
• Elevates ribs
• Muscle of
inspiration
Serratus Posterior Inferior Muscle
• Also stabilizes lower ribs
• Muscle of expiration
Intrinsic Back Muscles
• 3 layers of muscles
– Superficial layer
• splenius muscles
– Intermediate layer
• erector spinae muscles
– Deep layer
• Transversospinalis muscles
• Other deep muscles
Splenius muscles (100,101)
• Splenius capitis muscle
• Splenius cervicis muscle
• Nerve: PPR of cervical nerves
• Actions:
– Splenius cervicis muscle – neck
– Splenius capitis muscle – neck and head
• Unilateral action
– Lateral flexion of head and neck
– Ipsilateral rotation
• Bilateral action
– Extend head and neck
Erector spinae muscles (80-83)
• Innervated by posterior primary rami
• Located in groove between the spinous
processes and the angle of the rigs
• Arranged in 3 vertical columns
– Spinalis muscles (most medial)
– Longissimus muscles
– Iliocostalis muscles (most lateral)
• Each column is also divided into 3
muscles based on superior attachments
Spinalis
muscles
Longissimus Iliocostalis
muscles
muscles
Capitis
(head)
X
X
Cervicis
(neck)
X
X
X
Thoracis
(trunk)
X
X
X
Lumborum
(Lower
back)
X
Functions of erector spinae
muscles
• Bilateral contraction
– Extension of spine
– Control flexion
• Unilateral
– Lateral flexion of neck and back
– Ipsilateral rotation
• Longissimus capitis muscle
– Also ipsilateral rotation of head - unilateral
• Longissimus lumborum muscle
– Also Anterior tilt of pelvis - bilat
Deep layer of intrinsic muscles
• Just deep to the erector spinae muscles
• Transversospinalis muscles
– Semispinalis muscles
– Multifidis muscles
– Rotatores muscles
• Intertransversarii muscles
• Interspinalis muscles
• Levator costarum muscles
Transversospinalis muscles
• Nerve: PPR
• Attach to the transverse process of one
vertebrae and the spinous process of a
superior vertebrae
Transversospinalis muscles
•
•
•
•
Rotatores brevis – 1 level
Rotatores longus – 2 levels
Multifidis – 2-4 levels
Semispinalis – 5 to 7 levels
– Semispinalis capitis
– Semispinalis cervicis
– Semispinalis thoracis
Actions of transversospinalis
muscles
• Unilateral
– Contralateral rotation of head and/or spine
• Bilateral
– Extension of spine
• Semispinalis
– Extend head and spine
– Lateral flexion
• Multifidis (S4 to C2)
– Do not extend the skull
– Stabilize vertebrae
– Lateral flexion
• Rotatores (brevis and longus)
– Stabilize vertebrae
Intertransversii muscles
• Located between adjacent transverse
processes
– Poorly developed in thoracic region
– Well developed in lumbar and cervical regions
• Innervation: APR and PPR
• Function
– Unilateral: lateral flexion
Interspinalis mm
• Located between spinous processes of
adjacent vertebrae
– Not present throughout most of thoracic
region
• Innervation: PPR
• Function
– Extension of vertebral column
Levator costarum mm.
•
•
•
•
O: Transverse processes of C7 to T11
I: Rib below vertebrae of origin
Innervation: PPR
Function
– Elevates ribs, assists in inspiration
Suboccipital Region
• Located between the skull and the upper
spinal cord
• Includes
– Muscles and joints deep to the trapezius and
the semispinalis capitis muscles
• Located between occipital bone and the
posterior aspects of C1 and C2
Joints of the suboccipital region
• 2 joints
– AO
– AA
Suboccipital Muscles
• 4 small muscles in the suboccipital region
– Mainly postural
– May act more as proprioceptive sensors
rather than as movers
• However, we will cover movements of these
muscles
– ALL innervated by the suboccipital nerve from
the PPR of C1
Rectus capitis posterior major mm.
• O: Spine of C2
• I: Lateral part of inferior nuchal line of the
occipital bone
• F:
– Unilateral
• Rotates head to same side at AA joint
• Ipsilateral flexion of head at AO joint
– Bilateral: Extension at AO joint
Rectus capitis posterior minor mm.
• O: posterior tubercle of atlas (C1)
• I: Occipital bone: medial inferior nuchal
line
• F:
– Bilateral: Extension of head at AO joint
Obliquus capitis inferior mm.
• O: spine of C2
• I: transverse process of C1
• F:
– Rotates the atlas and skull as a unit to the
same side
Obliquus capitis superior mm.
• O: transverse process of C1
• I: Occipital bone above inferior nuchal line
• F:
– Unilateral: Lateral flexion of head
– Bilateral: Extension
Suboccipital Triangle
• Important region
which contains
– Vertebral artery
– Suboccipital nerve
(PPR of C1)
Roof of suboccipital Triangle
• Semispinalis
capitis muscle
Floor of suboccipital Triangle
• Posterior
atlanto-occipital
membrane
• Posterior arch
of C1
Borders of the suboccipital triangle
• Superomedial
– Rectus capitis
posterior major
muscle
• Inferolateral
– Obliquus capitis
inferior muscle
• Superolateral
– Obliquus capitis
superior muscle