Back Muscles

Iliocostalis

- The most lateral column of the erector spinae group - three parts have their origin and or insertion on the ribs -associated with the ribs. -three parts: Iliocostalis lumborum Iliocostalis thoracis Iliocosatlis cervicis

Superficial layer

- erector spinae (all three subgroups) - splenius muscles

Intermediate layer

- two parts of Transversospinalis (Semispinalis & multifidus)

superficial back muscles description

-*axioappendicular* muscles -*extrinsic* layer of muscles -Attach the upper limb (appendicular skeleton) to the axial skeleton -originate from the bony structures of the back and insert on the bones of upper limb. -act to move the upper limb and not the back -intervated by *ventral primary rami* not dorsal primary rami.

intermediate back muscles Description

-*extrinsic* back muscles -involved in the act of respiration by acting on the chest wall. -innervated by the *ventral primary rami

Latissimus dorsi description

-Very broad flat muscle -Covers inferior half of the back (T6 to iliac crest) -Attaches the upper limb to the trunk -Acts on the shoulder joint

Longissimus

-Intermediate division -associated with the transverse processes of vertebrae -The lowest section is the longissimus thoracis (there is no lumborum part) -Lower part of this muscle blends with iliocostalis lumborum

Vertebral column Rotation

-Multifidi, Rotatores and Semispinalis muscles rotate the trunk to the opposite side -Splenius muscles and the Erector spinae extend the trunk and help to rotate it to the same side -Oblique capitis inferior and rectus capitis posterior major and minor rotates the atlas and turns the face to the same side -The oblique capitis superior and the rectus capitis posterior major and minor extend the head bilaterally and flex it to the same side unilaterally

Latissimus dorsi Action

-Pulls arm posteriorly (extends arm) and rotates medially -Used in chopping wood or crawl stroke in swimming -It adducts, extends and medially rotates the humerus at the shoulder joint -Along with the pectoralis major it is a powerful adductor of the arm

deep back muscles description

-true (*intrinsic*) muscles of the back. -primary movers of the back. -All innervated by the *dorsal primary rami*. (only muscles) •Originally have a segmental arrangement and only extend from one vertebra (segment) to the next. •As a group extend from the skull to the pelvis covered by the deep fascia •origins and insertions of different muscles overlap, the entire vertebral column moves smoothly during flexion, extension and rotation •act to maintain posture, balance & various movements (flexsion, extension, rotation) •most of body weight is anterior to the vert column, many support the body weight by extending the vert column. •Vertebral transverse & spinous processes provide places for attachment •many are very long & cross more than 1 segment of the vert column and are innervated by more than 1 spinal cord level. •Majority have multiple origins and insertions

Back strains

Results from extensive extension and rotation - results in microscopic tearing of muscle cells or ligaments

Erector spinae (Sacrospinalis) attachment

Sacrum iliac crest spinous process of lumbar and last two thoracic vertebrae

Intertransversarii

Segmental muscles Run vertically between adjacent transverse processes. Well developed in cervical and lumbar regions Lacking in thoracic region.

Rotatores

Segmental muscles Have a single origin and a single insertion unlike most other back muscles. Span one or two vertebrae Best developed in the thoracic region Two sets: Long rotatores (Longus) Short rotatores (Brevis)

Deep layer

Segmental muscles and suboccipital muscles

intermediate back muscles (ex)

Serratus posterior superior Serratus posterior inferior

Vertebral column Flexion

Anterior trunk muscles Gravity Back muscles act as antagonistic - relax gradually to produce a smooth movement

Dermatomes

Area of the skin innervated by fibers from a single spinal nerve or spinal cord segment Dermatome maps have been developed from clinical studies Adjacent dermatomes overlap Dermatome maps can be used for clinical sensory testing

Rhomboid major and minor description

One sheet of muscle, lies deep to the trapezius m

Investing layer

deep fascia - invests (covers) deeper structures. Extensions from the deep surface of the deep fascia invests deeper structures such as muscles and neurovascular bundles

Latissimus Dorsi (layer)

deep layer of superficial muscle group

Rhomboids (layer)

deep layer of superficial muscle group

levator scapula (layer)

deep layer of superficial muscle group

Epaxial

dorsal Deep extensor muscles of the back

suboccipital nerve suply

dorsal ramus of C1 (suboccipital) nerve.

Trapezius nerve injury

drooping of scapula (shoulder) also known as shoulder drop To test its strength the shoulder is shrugged against resistance

Iliocostalis lumborum

from common tendon to ribs 6-12

Iliocostalis thoracis

from lower 6 ribs to upper 6 ribs

Iliocosatlis cervicis

from ribs 3-6 to transverse process of C4 - C6

Longissimus capitis

from the tendon of insertion of longissimus cervicis to the mastoid process

Trapezius Action

holds upper limb to trunk adducts (retract) scapula- middle fibers raises scapula (upper fibers) depresses scapula rotates scapula so that the inferior angle is moved laterally for abduction of upper limb above horizontal position

Semispinalis capitis

inserts on the occipital bone

Serratus Posterior Inferior (layer)

intermediate muscle

Serratus Posterior Superior

intermediate muscle

Longissimus thoracis

largest part (common tendon to lower 9 ribs)

Trapezius Innervation

motor: cranial nerve XI (spinal accessory nerve) pain and porprioception: C3 and C4 (ventral primary rami)

suboccipital triangle

oblique capitis inferior, oblique capitis superior and the rectus capitis posterior major

Trapezius Insertion

occipital &cervical fibers: clavical (lateral 1/3) lower cervical &upper thorasic fibers: acromion and spine of the scapula lower fibers: scapular spine

Serratus posterior superior Nerve

First three thoracic spinal nerves

Trapezius Origin

Occipital bone, ligamentum nuchea, spinous process C7 - T12

Superficial fascia

(teal subcutanea) Subcutaneous tissue (tissue immediately below the skin) Found between the skin and the deep fascia Covers most of the body Storage area for body fat Not very well organized

deep back muscles (ex)

*Superficial Layer* -Splenious -Splenius Capitis -Splenius Cervicis -Erector Spinae -Illiocostalis -Illiocostatlis Lumborum -Illiocostatlis Thoracis -Illiocostatlis Cervicis -Longissimus -Longissimus Thorasics -Longissimus Cervicis -Longissimus Capitis -Spinalis *Intermediate Layer* -Semispinalis -Semispinalis Thoracis -Semispinalis Cervicis -Seimspinalis Capitis -Multifidus *Deep Layer* -Segmental Muscles -Interspinalis Set -Intertransversarii Set -Rotatores Set -Long Rotatores (Longus) -Short Rotatores (Brevis) -Subocipital Muscles -Oblique Capitis Inferior -Oblique Capitis Superior -Rectus Capitis Posterior Major -Rectus Capitis Posterior Minor

nerves supplying the epaxial division muscles

*dorsal primary* rami of spinal nerves

nerves supplying the hypaxial division

*ventral primary rami*

The greater occipital nerve

- (dorsal ramus of C2) -emerges from below the oblique capitis inferior muscle (outside the triangle). - crosses the muscle and travels obliquely across the triangle to the back of the skull -This is a sensory nerve to the posterior part of the scalp. - does *not* provide innervation to any of the muscles of the triangle

Latissimus dorsi Nerve injury

Unable to raise the trunk with the upper limbs during climbing

rhomboid minor

Upper part

Short rotatores

(Brevis) Found in the lumbar, thoracic and cervical areas. Attach to the vertebra above (do not skip a vertebrae

Erector spinae group description

(Sacrospinalis) •Largest muscle mass of the back. •prominent bulge on each side of the lower part of the vertebral column between the spinous process and the angle of ribs. •Chief extensor of the vertebral column •In the lumbar region it divides into the following 3 vertical columns: *Iliocostalis* *Longissimus* *Spinalis* •Each column is further divided into three parts according to its superior attachments •The muscle of each part is made up of overlapping short muscle fibers to provide smooth controlled action

Levator scapulae description

-A strap-like muscle located in the neck and the upper part of the thorax -The upper part lies deep to the sternocleidomastoid and the inferior part lies deep to the trapezius muscles

Trapezius Description

-Flat triangular muscle .-Covers back of neck and upper half of the trunk -The two muscles, one on each side of the vertebral column, form a trapezoid (4 sided) structure - Provides direct attachment of pectoral girdle to the axial skeleton (trunk) skull and vertebral column -Helps to suspend the upper limb from the trunk -Muscle fibers are divided into three parts

vertebral artery

-originates at the base of the neck from the sunclavian artery and passes superiorly through the transversae foramina of cervical vertebrae. - It enters the suboccipital triangle and by coursing across the floor of the triangle enters the skull through the foramen magnum.

Serratus posterior inferior Action

Aids in respiration by holding ribs steady when diaphragm moves up

Serratus posterior superior Insertion

2nd to 4th ribs

Semispinalis thoracis

?

Vertebral column Extension

All deep back muscles except intertransversarii Erector spinae acts as the chief extensor muscle

Triangle of auscultation

A small triangular gap between muscles near the inferior angle of scapula. Bounded by trapezius, latissimus dorsi and medial border of scapula A good place to listen for the respiratory sounds with a stethoscope The respiratory sounds here are less muffled

Rhomboids Action

Adduct scapula Rotate scapula so the glenoid cavity moves inferiorly

Semispinalis cervicis

C2 spine highest level of insertion

Retinaculum

Deep fascia- thickening of the deep fascia across tendons of muscles at joints

Intermuscular septa

Deep fascia- separates muscles into groups

Rhomboids Blood Supply

Dorsal scapular artery

Levator scapulae Blood Supply

Dorsal scapular artery (branch of axillary a) opr deep branch of transverse cervical a

Levator scapulae Nerve

Dorsal scapular nerve (C5) and 3rd & 4th cervical nerves

Rhomboids Nerve

Dorsal scapular nerve (ventral ramus of C5) and some fibers from C4

Serratus posterior superior Action

Elevates ribs

Levator scapulae Action

Elevates scapula Rotates scapula to move the glenoid cavity and shoulder joint inferiorly

Latissimus dorsi Insertion

Humerus (intertubercular groove) - between Teres major and Pectoralis major

Rhomboids nerve injury

Injury to the dorsal scapular nerve results in inability to adduct the scapula

Vertebral column Lateral flexion

Intertransversarii Splenius capitis and cervicis rotate the head to the same side and laterally flex the neck Erector spinae initiates lateral flexion unilaterally All muscles on the opposite side control flexion by relaxing gradually

Suboccipital muscles

Intrinsic deep muscles This group of muscles do not follow the above pattern They are responsible for movement of the head and neck only assist with head movements

Splenius group

Intrinsic deep muscles arise from the posterior midline of the back and proceed laterally and superiorly to their insertion. found in the back of the neck and they mainly assist with head movements

Erector spinae group

Intrinsic deep muscles arise from the posterior midline of the back, or more laterally, and runup longitudinally

Transversospinalis group

Intrinsic deep muscles arise laterally but travel toward the midline to their insertion

Serratus posterior inferior Nerves

Last four thoracic nerves

Serratus posterior superior Origin

Ligamentum nuchae and spines of C7 to T3 vertebrae

Serratus posterior superior description

Located deep to rhomboid muscles

Long rotatores

Longus Found in the lumbar, thoracic and cervical areas. They skip a vertebra.

Serratus posterior inferior Insertion

Lower four ribs

rhomboid major

Lower, bigger part

Rhomboids Insertion

Medial border of scapula

Rhomboids Origin

Spines of lower cervical (C7) and upper thoracic (T1 - T5) vertebrae

Latissimus dorsi Origin

Spinous process of lower six thoracic vertebrae Thoracolumbar fascia Iliac crest and lower 3 or 4 ribs

Deep fascia

Strong, dense, well organized layer of connective tissue Located deep to the superficial fascia and contains no fat Where muscles attach to bones the deep fascia becomes continous with periosteum Helps form compartments in the body Divides into 3 layers

Trapezius (layer)

Superficial layer of superficial muscles of the back

Levator scapulae Insertion

Superior angle of scapula and along its upper medial border

Serratus posterior inferior Origin

T11 to L2 vertebral spines

Suboccipital muscle group

This group connects the skull to the atlas and axis. There are 2 obliquely oriented and 2 straight muscles. Oblique capitis inferior Oblique capitis superior Rectus capitis posterior major Rectus capitis posterior minor

Latissimus dorsi Blood supply

Thoracodorsal artery

Latissimus dorsi Nerve supply

Thoracodorsal nerve (C6, C7, C8 level of spinal cord) from the brachial plexus

Longissimus cervicis

Transverse process of T1-T5 to Transverse process of C2-C6

Levator scapulae Origin

Transverse processes of first three or four cervical vertebrae

Multifidus

Transversospinalis •Deeper to semispinalis •Thickest in lumbar area. •Present throughout the back •Muscle fibers go from Transverse to spinous processes •Individual segments are not know by separate names •Ends in the cervical region. •The different parts are not usually distinct. •In sacral and lumbar areas the muscle is covered by erector spinae. •In the thoracic and cervical regions it is covered by semispinalis. •Muscle fibers cover 2 - 4 vertebrae.

Segmental muscles

Transversospinalis •Deepest part of transversospinalis group •Better developed in cervical and lumbar regions •Lie deep to the multifidus Three sets 1. Interspinalis 2. Intertransversarii 3.Rotators

Semispinalis

Transversospinalis •Muscle fibers arranged longitudinally like the erector spinae group. •Muscle fibers span over about 4-6 vertebrae •Lacking in the lumbar region •Lie superficial to the multifidus -semispinalis thoracis, cervicis, and capitis

Trapezius Blood Supply

superficial branch of the transverse cervical artery located on deep surface of the muscle

Trapezius (layer)

superficial layer of Superficial muscle group

Superficial back muscles (ex)

superficial layer-Trapezius deep layer- Latissimus dorsi Levator scapulae Rhomboid major and minor

hypaxial

ventral 1.Infrahyoid 2.Flexor muscles of vertebral column 3.Quadratus lumborum

Erector spinae (Sacrospinalis) origin

very extensive *common tendon of origin*

erector spinae group Action

•Bilaterally extend the head and vert column. •Unilaterally laterally flex the head and vert column. •*chief extensor of the vertebral column.*

Splenius capitis

•Broad flat muscle of the neck •Partly covered by the trapezius and the sternocleidomastoid •Upper and larger of the two splenius muscles •Fibers proceed superiolaterally from their origin (ligamentum nuchae, spines of upper thoracic vertebrae) to attach to the skull (occipital bone, mastoid process)

development of muscular system

•Develop from mesoderm germ layer •Each somite differentiates into a sclerotome and a myo - dermatome •The myotome region of myo - dermatome gives rise to myoblast cells (embryonic muscle cells) that form the muscles of the trunk •Myotomes divide into a Epaxial (dorsal) division Hypaxial (ventral) division •Even though most of the myoblasts migrate away from their specific myotome level of origin, they always maintain their original nerve supply from that segment •During development fusion between adjacent segments takes place to form larger muscle masses covering more than one segment. •Sequential splitting of muscles takes place later to form different superimposed layers.

Splenius group

•Group consists of only 2 muscles •Most superficial intrinsic muscles of the posterior part of the neck •Muscle fibers arise from the midline and run superiorly and laterally •splenius =bandage-like structure •the muscle represents a bandage wrapped around the neck -Splenius capitis & Splenius cervicis

Spinalis

•Most medial and smallest division of erector spinae •Poorly developed in most individuals •Usually only the thoracic part is present •In well developed individual it extends from the thorax to the skull and contains a thoracis, cervical and a lumbar segment. •spinous processes of lumbar vertebrae to spinous processes of upper thoracic vertebrae

Splenius cervicis

•Narrow muscle located below and parallel to the splenius capitis •Fibers extend superiorly and laterally - from spinous processes of upper thoracic vertebrae (T3-T6) and insert at the transverse processes of upper cervical vertebrae (C2-C4) •No fibers attach to the skull

Interspinalis

•Segmental muscles Well developed in cervical and lumbar regions. •Lacking in thoracic region •The muscles are separated by interspinous ligaments •Stretch between adjacent spinous processes from C2 to T1.

Transversospinalis muscle group

•deeper to the erector spinae group •Shorter than erector spinae •Slant inward from their origin to their insertion •Originate from transverse processes and proceed to spinous processes of more superiorly located vertebrae •Consist of three muscle masses: Semispinalis Multifidus Segmental muscles