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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