11. muscles of the back

8/10/2019 11. Muscles of the Back

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BACK

Alexis Maharaj & Lakshmi K. Tiwari


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INTRODUCTIONThe back comprises the posterior aspect of the trunk, inferior to the necsuperior to the buttocks . It is the region of the body to which the head,limbs are attached. The back includes the:

o Skin and subcutaneous tissue

o Muscles

o Vertebral column

o Ribs (in the thoracic region)

o Spinal cord and meninges

o Various segmental nerves and vessels.

oThe muscles of the back are divided into two groups; extrinsicand intmuscles

NB: Classification depends on embryological origin and innervation


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EXTRINSIC GROUP OF MUSC


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oGenerally innervated by anterior rami of spiral nerves

oSubdivided into two groups: superficialand intermediate

oEmbryological origin: areas other than the back

oSuperficial group:trapezius, levator scapulae, latissimus dorhomboid major, rhomboid minor

oAids in movement of upper limbs

oIntermediate layer: serratus posterior superior, serratus posinferior

oAids in movement of thoracic wall and in respiratory functio


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Superficial Muscles


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oSometimes called appendiculargroup

oLocation: deep to the skin and superficial fascia(layer of tis

beneath the skin)

oFunction: attach superior part of appendicular skeleton (clascapula, humerus) to axial skeleton (vertebral column, skull,

oIn the superior part of back: rhomboid minor, rhomboid malevator scapulae are all located deep to the trapezius muscle


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Trapezius Muscle

oGroup of flat, triangular muscles collectively referred to as tmuscle

oBase of triangle is at the vertebral column (point of origin) aapex points toward the tip of shoulder (point of insertion)

oMuscles on either side of vertebral column form a trapezoid

oSuperior fibres (skull and upper portion of vertebral columnto attach to the lateral third of clavicle and acromion of scap


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oContractionof the superior fibres elevatethe scapula

oInferior and superior fibres work together to rotatelateral a

scapula upward(e.g. when raising the upper limb above the

oInnervated byspinal accessory nerve XI which descends froneck on to the deep surface of the muscle

oProprioceptive fibres from the trapezius pass into branchescervical plexus and enter the spinal cord at levels C3 and C4


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Latissmus Dorsi

oLarge, flat, triangular muscle

oBegins in lower portion of back and gradually narrows as it to a tendon that attaches to the humerus anteriorly

oMovements of the muscle are extension, adductionand me

rotation of the upper limb

oInnervated by thoracodorsal nerve


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It can depress the shoulder preventing upward movement

Latissmus d


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Levator ScapulaeoSlender muscle

oDescends from transverse process of the upper cervical verthe superior angle on the medial border of the scapula

oElevatesthe scapula and may assist the other muscles in rolateral aspect of the scapula inferiorly

oInnervated by branches from the anterior rami of spinal nerand C4and the dorsal scapular nerve


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Levator scapu


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Rhomboid Minor

oInferior to levator scapulae and superior to rhomboid majo

oSmall cylindrical muscle

oArises from the ligamentum nuchae of the neck and the spi

processes of CV II and TI and attaches to the medial scapulaopposite the root of the spine


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Rhomboid Major

oOriginates from the spinous process of the upper thoracic vand attaches to the medial scapular border (inferior to the rminor)


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Rhomboid Minor & Major

o

Work together to retract or pull the scapulatoward the vercolumn

oAids other muscles in inferiorly rotating the lateral aspect oscapula

oInnervated by the dorsal scapular nerve


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Superficial Extrinsic Muscle

Muscle Origin Attachment Inner

Trapezius Vertebral column Lateral third of clavicle,

acromion

Access

Latissmus dorsi Lower back Humerus Thorac

branch

Levator Scapulae Transverse processes of

superior cervical vertebrae

Superior Angle of medial

scapular border

Anteri

nerves

scapulRhomboid major spinous process of the upper

thoracic vertebrae

medial scapular border Dorsal

Rhomboid minor ligamentum nuchae and the

spinous processes of CV II

and TI

medial scapular border Dorsal


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Intermediate Muscles

Serratus posterior super

serratus posterior inf


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Serratus Posterior Superior

oDeep to rhomboid muscle

oFibres descendto attach toupper ribs

Serratus Posterior Inf

oDeep to latissimus dor

oFibres ascendto attacribs


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Serratus Posterior Superior & Infe

oPasses obliquely outward from the vertebral column to atta

oElevateand depressthe ribs

oReferred to as respiratory group

oInnervated by segmental branches of anterior rami of intercnerves


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Serratus posterior sup

Serratus posterior


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Muscle Origin Attachment Innerva

Serratus Posterior

Superior

Spinous processes of lower

cervical and upper thoracic

vertebrae

Upper ribs anterior

intercost

Serratus Posterior

Inferior

Spinous processes of lower

thoracic and upper lumbar

vertebrae

Lower ribs anterior

intercost

Intermediate Extrinsic Muscle


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INTRINSIC/ TRUE GROUP OFMUSCLES


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oGenerally innervated by posterior rami of spinal nerves

oSubdivided into three groups: superficial, intermediate andd

oEmbryological origin: epaxial division of the myotome

oSometimes called true back muscles

oLocation: at the vertebral column, from the pelvis going up tohead


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oSuperficial group: Splenius Capitis, Splenius Cervicis

oAids in lateral flexion, rotation and extension of the head and

oIntermediate layer (Erector spinae muscles): Iliocostalis, LonSpinalis

oAids in movement and extension of vertebral column

oDeep layer: Semispinalis, Multifidus, Rotatores

oAids in connection of transverse and spinous processes, ,aintposture, assist in movement


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Superficial/ SpinotransversalesMuscles


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Muscle Origin Attachment Innerv

Splenius capitis Ligamentum nuchae, spinesof C7-T6 vertebrae

Mastoid process, beneath

superior nuchal line

Posterio

spinal n

Splenius cervicis Ligamentum nuchae, spinesof C7-T6 vertebrae

Transverse processes of

C1-C3

Posterio

spinal n

Superficial Intrinsic Muscles


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Intermediate/ Erector Spinae Mus


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Muscle Origin Insertion Innerva

Iliocostalis Iliac crest, sacrum Inferior borders of rib

angles

Posterior

of spinal

Longissimus Transverse processes of

lumbar vertebrae

Mastoid process, ribs

to cervical and thoracic

transverse processes

Posterior

of spinal

Spinalis Spinous processes ofthe upper lumbar and

lower thoracic

vertebrae

Upper thoracic spinousprocesses, base of skull

Posteriorof spinal

Intermediate Intrinsic Muscle


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Muscle Origin Attachment Innerv

Semispinalis Transverse processes of cervical and

thoracic vertebrae

Spinous processes of

4-6 vertebrae aboveorigin

Posteri

rami ofC2

Multifidus posterior sacrum, posterior superior

iliac spine, Transverse processes of

T1-T3, articular processes of C4-C7,

mammillary processes of the lumbar

vertebrae

Spinous processes of

2-4 vertebrae above

origin

Posteri

rami of

nerves

Rotatores Transverse processes of vertebrae Junction of the

transverse/ spinous

process and lamina

Posteri

rami of

nerves

Deep Intrinsic Muscles

Th l b F i


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Thoracolumbar Fascia

oCovers the deep muscles of the back

oAbove, it passes anterior to serratus posterior superior

oMedially attaches to the thoracic vertebrae spines, and lateralangles of the ribs.


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oIn the lumbar region there are 3 layers:

Posterior layer- attached to the spines of the lumbar and sacraand supraspinous ligaments.

Middlelayer-attached lumbar transverse processes and theintertransverse ligaments, the iliac crest, and the inferior borde12th rib and lumbocostal ligament.

Anterior layer-covers quadratus lumborum

oThe posteriorand middlelayers form a tough seam at the latmargin of erector spinae


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REFERENCES


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REFERENCESoGilroy, MacPherson, Ross, 2012, Atlas of Anatomy, 2 ed, Thie

Medical Publishers, Virginia.

oGray Henry, 2012, GraysAnatomy, 15 ed, Octopus PublishinLtd, London.

oStranding, Borley et al, 2009, GraysAnatomy: The Anatomicof Clinical Practice, 40 ed, Elsevier, London.

oR. L. Duke, A. W. Wogl, A. W. M. Mitchell, 2013, GraysAnatoStudents, 3rdedition, Elsevier, Canada

11. muscles of the back

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