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Back and vertebral column
Overview of back and vertebral column
Back
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Posterior aspect of the trunk; inferior to neck, superior to buttocks
Head neck and limbs attach
Includes
o Skin and subcutaneous tissue
o Superficial and deep layers of muscles
o Vertebral column
o Ribs
o Spinal cord and meninges
o Segmental nerves and vessels

Vertebral column
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Comprised of the vertebrae and intervertebral (IV) discs
Skeleton of neck and back; main part of axial skeleton
Functions
o Protection of spinal cord and spinal nerves
o Support weight of body superior to pelvic level
o Rigid and flexible axis for body
o Extended base for the head to rest and pivot
o Posture and locomotion

Vertebrae
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Vertebral column consists of 33 vertebrae arranged in 5 regions: cervical (7),
thoracic (12), lumbar (5), sacral (5), and coccygeal (3)
Significant motion occurs only between the superior 25 vertebrae
In adults, the sacral vertebrae fuse to form the sacrum and the coccygeal
vertebrae fuse to form the coccyx
Lumbosacral angle is the junction of lumbar and sacral regions
Vertebrae increase in size to a max at the end of the lumbar section, then
decrease in size; size is relative to the weight that each vertebrae has to bear
o From the sacrum onwards, weight bearing is transferred to pelvic girdle
Flexible structure due to presence of multiple small bones separated by IVs
o Movement between each vertebrae is small, but aggregates to form a
flexible yet rigid column

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Regional characteristics of vertebrae
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Each vertebra unique, but have characteristic features of each region
Some individual vertebrae also have distinguishing features
In each region the articular facets orient on the articular processes in a
characteristic direction; determines type of movement between adjacent
vertebrae and the region as a whole

Cervical vertebrae
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Skeleton of the neck; located between cranium and thoracic vertebrae
Smallest of the 24 moveable vertebrae
Greatest range and variety of movement of all the vertebral regions, due to
o Thick IV discs relative to vertebrae size
o Near horizontal orientation of the articular facets
o Small amount of surrounding body mass

Thoracic vertebrae
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Skeleton of the upper back, provide attachment for ribs
Type of movement in this region
o Rotation and some lateral flexion, permitted by vertically extending
spinous processes with vertical facets
o Limited flexion, extension and lateral flexion, due to attachment of
ribcage, vertically oriented facets, and overlapping spinous processes
T1-T4 have some features of cervical vertebrae and T9-T12 have some
features of lumbar vertebrae

Lumbar vertebrae
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Skeleton of the lower back, between thorax and sacrum
Type of movement permitted in this region is flexion, extension and lateral
flexion, but no rotation
o Laterally facing facets of the inferior articular processes articulate with
the medially facing facets of the superior articular processes of the
vertebra below
L5 is the largest of all moveable vertebrae
o Carries the weight of the entire upper body
o Taller anteriorly than posteriorly, thus largely responsible for the
lumbosacral angle

Cervical

Thoracic

Lumbar

Small, wider laterally than anteroposteriorly
Superior surface concave, with uncus of
the body; inferior surface convex
Large and triangular

Heart shaped, 1/2 costal facets for
articulation with head of rib

Large, kidney shaped

Circular, smaller than foramen of
cervical and lumbar
Long, strong, extend
posterolaterally
Length decreases T1-T12
T1-T10 have facets for articulation
with rib tubercles

Triangular, larger than thoracic and
smaller than cervical
Long and slender
Accessory process on posterior surface
(muscle attachment)

Superior facets face
posterolaterally
Inferior facets face
anteriomedially
Articular facets nearly vertical
Long, slope posteroinferiorly;
overlap vertebra below

Superior facets face posteromedially
Inferior facets face anterolaterally
Mammillary process on posterior
surface of each superior process
(muscle attachment)
Short and sturdy; thick, broad, hatchet
shaped

Image

Body

Foramen
Transverse
process

Articular
process

Spinous
process

Transverse foramina: vertebral arteries and
veins pass through
Anterior and posterior tubercles: levator
scapulae and scalenes attach
Grooves for spinal nerves are located
between the tubercles
Superior facets face superoposteriorly
Inferior facets face inferoanteriorly
Oblique facets almost horizontal
Generally short and bifid

Images taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...
Complete costal facet on superior edge to articulate with first rib and
demifacet on inferior edge articulates with second rib
Superior half is thoracic in character (costal facets and articular processes for rotary movement)
Inferior half is lumbar in character (no costal facets, articular processes for flexion and extension only)
Experiences transitional stresses; most commonly fractured vertebra

T1
T12

Widest of the cervical vertebrae
No body or spinus process
Paired lateral masses bear the weight
of the cranium; their superior articular
surfaces of the lateral masses
articulate with occipital condyles
...
Each arch has a
tubercle
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Sacrum
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Located between hip bones
Wedge shaped, composed of five fused sacral bones in adults
o Wider in proportion to length in females, but body of S1 larger in males
Supports vertebral column and forms the posterior part of the bony pelvis
o Tilted, articulates with L5 at the lumbosacral angle (130-160o)
Superior half is weight bearing, inferior half is not
Provides strength and stability to the pelvis – transmit weight of the body to
the pelvic girdle
Pelvic girdle – bony ring formed by the hip bones and sacrum, to which the
lower limbs attach
Sacral canal – continuation of vertebral canal in the sacrum
o It contains the cauda equina (spinal nerves that arise inferior to L1)
Four pairs of sacral foramina located permit exit of the posterior and anterior
rami of the spinal nerves; anterior foramina larger than posterior
Base of the sacrum formed by superior surface of S1; superior articular
processes articulate with inferior articular processes of L5
Sacral promontory – anterior projecting edge of the body of S1
o Important obstetric landmark
Apex of the sacrum has an oval facet for articulation with the coccyx
Pelvic surface is smooth and concave
o Sacral bones separated by IV discs in children
o Four transverse lines where the sacral bones fuse (starts ~age 20 years)
Dorsal surface is rough and convex with five longitudinal ridges
o Median sacral crest – fused spinous processes of S1-S4 (S5 has no
spinous process)
o Intermediate sacral crests – fused articular processes
o Lateral sacral crests – tips of transverse processes
Sacral hiatus – u-shaped structure formed due to lack of S5 (and sometimes
s4) spinous processes; leads into the sacral canal
Sacral cornua – inferior articulating process of L5, project either side of hiatus
Auricular surface – superior part of the lateral surface
o Site of the synovial part of the sacro-iliac joint
o Covered with hyaline cartilage

Coccyx
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Coccyx is the small triangular bone formed from fusion of 4 coccygeal bones
o Co1 may remain separate from the fused group, and with increasing
age may fuse with the sacrum
Remnant of the embryonic tail-like caudal eminence
Pelvic surface is concave and smooth
Posterior surface has articular processes
Co1 is largest and broadest
o Transverse processes connect to the sacrum

Articular processes form coccygeal cornua, which articulate with the
sacral cornua
Does not support body weight when standing, may flex anteriorly when sitting
– possibly receiving some weight
Provides attachment for gluteus maxiumus, coccygeus muscles and
anococcygeal ligament
o

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Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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5cm superior to the anus

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Variations in vertebrae
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Most people have 33 vertebrae; developmental errors can result in 32 or 34
Abnormal number of vertebrae above sacrum is 5-12%
Variations affected by race, gender and developmental factors
o Increased number of vertebrae more common in men and reduced
number more common in women
o Some races show more variation in vertebrae than others
Variation in vertebrae may be clinically important

Increased length of presacral region increases strain on the inferior
lumbar region
o Most detected incidentally
Caution required when describing an injury
o When counting vertebrae start at base of the neck, as cervical
vertebrae stays constant
o Thoracic and lumbar regions should be considered together in the
event of variation as an e
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extra lumbar vertebra usually means one
less thoracic vertebra
Variations in vertebrae also involve the relationship with the ribs, and the
number of vertebrae that fuse to form the sacrum
o Cranial shift – 13 ribs, including cervical rib articulating with C7
o Caudal shift – 13 ribs, including a lumbar rib articulating with L1
o Sacralised L5 – L5 fuses with sacral bones
o Lumbarised S1 – S1stays separate from rest of sacrum
o

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Vertebral column
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Comprises the 33 vertebrae and other components forming the axis of the
body
Semirigid core around movements of the trunk occur – other soft structures
are at risk of damage (spinal cord, descending aorta, vena cavae,
oesophagus, thoracic duct)

Joints of the vertebral column
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Joints of the vertebral bodies
Joints of the vertebral arches
Craniovertebral joints (atlanto-axial and atlanto-occipital)
Costovertebral joints
Sacro-iliac joints

Joints of the vertebral bodies
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Symphyses (secondary cartilaginous joints) for weight bearing and strength
Articulating surface of adjacent vertebrae connected by
o IV discs
o Ligaments
IV discs provide strong attachment between vertebral bodies
o Comprise ~25% height of the column
o Permit movement and act as shock absorbers
o Two main components
 Annulus fibrosus
 Outer fibrous part, concentric fibrocartilage
 Oblique angle of the lamellae (layers) provide a tight
bond and allow limited rotation

o

o
o
o

 Vascularised peripherally, with sensory innervation
 Nucleus pulposus
 Gelatinous central mass
 Fluid nature permits flexibility and resilience
 Avascular
 Not central - more medioposterior as the annulus fibrosus
has fewer lamellae in the posterior region
Vertical forces deform the IV discs
 Broader when compressed, thinner when tensed/stretched
 Flexion causes compression and tension in the same disc
No IV disc between C1 and C2; most inferior disc is between L5 and S1
Thickness increases as you descend the column
Thickness relative to vertebral bodies is greatest in the cervical and
lumbar regions (to permit wide range of movement), also thicker
anteriorly in these regions

Image taken from Wikipedia, page Intervertebral Disc, available at
https://en
...
org/wiki/Intervertebral_disc

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Uncovertebral joints/clefts
o Can develop between the unci of bodies of C3/4-C6/7 and the
vertebrae above after age 10 years
o Located at the lateral and posteromargins of thee IV disc
o Covered with cartilage, with fluid contained in a capsule
o Frequent site of bone spur formation – pain

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Available at
http://www
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com/subject
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Available at
http://www
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Accessory ligaments of intervertebral joints
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Ligamenta flava - broad bands of elastic tissue joining the laminae of
adjacent vertebrae
o Meet in the midline
o Resist separation of the vertebral lamina by limiting quick flexion, thus
protecting the IV disc
o Preserve curvature of the column and assist with straightening after
flexion
Interspinous ligaments – weak, membranous ligaments connect adjoining
spinous processes (extend from root to apex)
Supraspinous ligaments – strong, fibrous ligaments connect tip of spinous
process from C7 to sacrum; merge with nuchal ligament at back of neck
Nuchal ligament – strong, broad fibroelastic ligament
o Extends from external occipital protuberance and posterior foramen
magnum to the spinous processes of the cervical vertebrae
Intertransverse ligament – connects adjacent transverse processes
o Scattered fibres in cervical region
o Fibrous cords in thoracic region
o Thin and membranous in lumbar region

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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com, PHARYNX, CRANIOVERTEBRAL JOINTS, PREVERTEBRAL REGION
STEVEN J
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Veins
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Spinal veins form venous plexuses along the vertebral column, inside and
outside the vertebral canal
o Internal vertebral venous plexus
o External vertebral venous plexus
Plexuses communicate through the intervertebral foramina
Basivertebral veins form within the vertebral bodies (large, torturous)
o Emerge from foramina on the surface of vertebral body’s and drain
anterior external and anterior internal venous plexuses
Intervertebral veins receive veins from spinal cord and vertebral venous
plexus as they accompany the spinal nerves through IV foramina to drain into
o Neck – vertebral veins
o Truck – segmental veins (intercostal, lumbar, sacral)

Image taken from Upright-health
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Available at
http://www
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com/vertebral-veins
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Intrinsic back muscles
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Comprise muscles of back proper and deep back muscles
Innervated by posterior rami of spinal nerves
Maintain posture and control movements of vertebral column
Extend from pelvis to cranium
Enclosed by deep fascia
o Attaches medially to
 Nuchal ligament
 Tips of spinous processes
 Supraspinous ligament
 Median crest of sacrum
o Attaches laterally to
 Transverse processes of cervical and lumbar
 Angle of ribs
Muscles grouped into superficial , intermediate and deep

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Available at http://muscular-system
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html

Superficial layer
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Splenius muscles are thick and flat, lie on posterior and lateral aspects of neck
Comprise the splenius cervicis and splenius capitis
Proximal attachment
o Nuchal ligament and spinous processes of C7-T6
Distal attachment
o S
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cervicis – transverse processes of C1-C3/4
Nerve supply is posterior rami of spinal nerve
Function
o Acting alone – lateral flexion of neck, rotate head
o Acting together – extension of head and neck

Intermediate layer
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Three erector spinae muscles – iliocostalis, longissimus, spinalis
Proximal attachment – tendon from posterior iliac crest, posterior sacrum,
carco-iliac ligaments, inferior lumbar spinous processes, supraspinous
ligament
Distal attachment
o Iliocostalis – three parts (lumborium, thoracis, cervacis); fibres attach to
angles of ribs and transverse processes of cervical vertebrae
o Longissimus – three parts (thoracis, cervicis, capatis); fibres attach to
ribs between tubercles and to the transverse processes of cervical,
and mastoid process
o Spinalis – three parts (thoracis, cervicis, capitalis); fibres attach above
spinous processes and to cranium

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Supplied by posterior rami of spinal nerves
Actions
o Acting bilaterally – extension of vertebral column and head, eccentric
contraction when flexed
o Acting unilaterally – lateral flexion

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Suboccipital and deep neck muscles
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Muscle compartment deep to the cervical region
Underlies trapezius, sternocleidomastoid, splenius and semispinalis
Pyramidal space inferior to external occipital protuberance
Includes posterior aspects of C1 and C2
Four small muscles deep to semispinalis capitis
o Rectus capitis posterior (major and minor)
o Two oblique muscles
All innervated by posterior ramus of C1 (suboccipital nerve)
Suboccipital triangle boundaries
o Superomedial – rectus captis posterior major
o Superolateral – obliquus capitis superior
o Inferolateral – obliquus capitis inferior
o Floor – posterior atlanto-occipital membrane, posterior arch C1
o Roof – semispinalis capitis
o Contents – vertebral artery, suboccipital nerve

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Contents of the vertebral canal
Spinal cord
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Protected by vertebrae, associated ligaments and muscles, spinal meninges
and CSF
Begins as continuation of medulla oblongata
Extends from foramen magnum to L2-L3 level
Tapering inferior end (conus medullaris) can terminate T12-L3; thus spinal cord
only in superior 2/3 of the vertebral canal
Enlarged in two regions in relationship to limb innervation
o Cervical enlargement C4-T1
 Most anterior rami form the brachial plexus
o Lumbosacral enlargement T11-S1
 Most anterior rami of lumbar and sacral plexi

Spinal nerves and nerve roots
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Spinal cord segment is the portion of spinal cord giving rise to the roots and
rootlets to form one bilateral pair of spinal nerves
Cervical spinal nerves (except C8) bear the same number as the vertebrae
forming the inferior margin of the IV foramina through which the nerve exits
Thoracic nerves onwards bear same number as vertebra forming superior
margin
Spinal cord occupies entire length in embryos, but during the foetal period,
the vertebral column grows faster than the spinal cord
o Cord ascends relative to the vertebral level
o Progressive obliquity of the nerve roots

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o Distance between origin and exit increases as you go down; thus
length of nerves also increase
Lumbar and sacral roots extend beyond L2, forming lose bundle of free
nerves (cauda equine) within lumbar cistern
From the tip of the conus medullaris, the filum terminale descends among the
spinal roots in the cauda equine
o Remnant of caudal part of the spinal cord
o Proximal end is filum terminl internum – vestiges of neural tissue,
connective tissue and neuroglia covered by pia mater
o Perforates inferior end of dural sac, gains layer of dura and continues
through sacral hiatus as filum terminal externum

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Segment level
Cervical

Number of nerves
8 (C1-C8)

Thoracic
Lumbar
Sacral

12 (T1-T12)
5 (L1-L5)
5 (S1-S5)

Coccygeal

1 (Co1)

Exit level
C1 nerve passes superior to arch of C1
C2-C7 nerves pass through IV foramina
superior to corresponding vertebrae
C8 nerve passes through IV foramina
betw C7 and T1
T1-L5 nerves pass through IV foramina
inferior to corresponding vertebrae
S1-S4 branch into anterior and posterior
rami in the sacrum; rami pass through
anterior and posterior sacral foramina
5th sacral and Co nerves pass via sacral
hiatus

Spinal meninges and CSF
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Spinal dura mater, arachnoid mater, and pia mater comprise the spinal
meninges
o Surround and support spinal cord, nerve roots and cauda equine
o Contain CSF

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
...


Spinal dura mater
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Outermost covering; tough fibrous tissue with some elastic
Separated from bones and ligaments of the vertebral canal by the epidural
space
o Contains internal vertebral venous plexus within epidural fat
o Runs length of the vertebral column from foramen magnum to sacral
hiatus and laterally to the IV foramina
Spinal dura forms the spinal dural sac – long tubular sheath; continuous with
cranial dura mater and anchored inferiorly to coccyx by filum terminale
Spinal dural sac is invaginated by posterior and anterior roots of the nerves,
forming tapering lateral extensions (dural root sheaths)
o Sheaths blend with epineurium
Innervated by the recurrent meningeal nerves – function unclear, some pain
receptors

Spinal arachnoid mater
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Delicate, avascular membrane made of fibrous and elastic tissue lining the
spinal dural sac and dural root sheaths
Encloses CSF filled space containing spinal cord, nerve roots and ganglia
Not attached to dura, but held against it by the CSF
o Dura-arachnoid interface
o Bleeding into it causes a subdural haematoma
Separated from the pia mater by subarachnoid space containing CSF
Arachnoid trabecular span the space and connect spinal arachnoid and pia

Spinal pia mater
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Thin, transparent innermost covering, closely follows surface of spinal cord
Covers roots of spinal nerves and spinal blood vessels
Continues as the filum terminale below the conus medullaris
Spinal cord suspended in the dural sac by the filum terminale plus right and
left denticulate ligaments (run longitudinally along each side of spinal cord)
Denticulate ligaments comprise fibrous sheet of pia extending midway
between posterior and anterior nerve roots from lateral sides of spinal cord
o Superior ones attach to cranial dura at foramen magnum
o Inferior ones attach to conus medullaris

Subarachnoid space
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Located between arachnoid and pia, contains CSF
Enlargement of this space at the lumbar cistern – L2 to S2
Dural root sheaths project from the side of the lumbar cistern

Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Image taken from Moore et al, Clinically Oriented Anatomy, Seventh Edition
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Reference
1
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Clinically Oriented Anatomy
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