Download Vertebral Column, Spinal Cord, and Deep Back

M1 – Gross and Developmental Anatomy
Vertebral Column, Spinal
Cord, and Deep Back
Dr. Krieg
Vertebral Column: Regions & Curvatures
Vertebral Column =
Stack of Articulated Vertebrae
•Synovial
Joints between
articular facets
•Intervertebral
disks between
vertebrae
•Spinal nerves
exit vertebral
canal via
Intervertebral
foramina
Prenatal C-Shaped Curvature
Infant is born with
curvatures which
are concave
anteriorly in all
regions of the
spine.
Secondary Curvatures Develop in
Cervical and Lumbar Regions
•As infant raises head to look
around, cervical curvature develops
concave posteriorly.
•Standing upright requires lumbar
curvature concave posteriorly.
•Abnormal Curvatures:
•Kyphosis: exaggerated thoracic
curvature resulting in humping
over
•Lordosis: accentuation of
lumbar curvature concave
posterior
•Scoliosis: Curvature to the side
Anterior Longitudinal Ligament
•Located Anterior
to the vertebral
bodies
•Resists Extension
of the spine
(bending backward)
Posterior Longitudinal
Ligament
•Located
Posterior to the
vertebral bodies
•Located
Anterior to the
spinal cord
•Resists Flexion
of the spine
(bending
forward)
Parts of a Typical Vertebra
•Body
•Arch:
•Pedicle
•Lamina
•Processes
•Transverse
•Spinous
•Articular facets
•Superior
•Inferior
•Vertebral
Foramen
Ligamenta Flava
•Atlas 12th ed, fig 4.24, p. 302
•Attached to laminae of contiguous vertebrae
•Prevent excessive flexion
•Pierced by spinal tap needle
Supraspinous & Interspinous
Ligaments
•Supraspinous
ligaments lie
Posterior to spines,
as if a strip of
“scotch tape” were
applied
•Interspinous
ligaments lie
between the spinous
processes
•Both resist flexion
Capsular Ligaments
•Surround the
joints between
superior and
inferior articular
processes
•Are generally lax
to permit free
gliding
movements
•Note the
intervertebral disks
between the bodies
of the vertebrae
Disks are Shock Absorbers
•Shape of disks
changes as force
is applied
•Fluid nucleus
pulposus is
incompressible
•Force is
distributed equally
in all directions,
preventing undue
concentration of
stress anywhere
on the vertebral
body
Intervertebral Disks
•Anulus fibrosis:
fibrocartilaginous
outer ring
•Nucleus pulposus:
semi-gelatinous
fluid mass
surrounded by
anulus fibrosus
•Reinforced by
anterior and
posterior
longitudinal
ligaments
•Least
reinforcement
posteriolaterally
Atlantooccipital and
Atlantoaxial Joints
•Base of skull is
formed by the
Occipital Bone
•1st vertebra = Atlas
•2nd vertebra = Axis
•Atlantooccipital
joint allows flexion
and extension: i.e.,
the “yes” joint
•Atlas pivots around
dens of axis hence
is the “no” joint
Atlantoaxial Joint
Dens represents
the body of the
Atlas
Anterior arch and
Transverse
Ligament of Atlas
form pivot around
the dens
Movements of the Spine are the Sum
of Movements between Vertebrae
Flexion
Extension Lateral Bending
Deep (True) Back Muscles
•Extend the back
•Located deep to
Thoracolumbar Fascia,
within a tight fascial space
•Developed in Back, not
immigrants
•Innervated Segmentally by
Dorsal Primary Rami
•Organized in Longitudinal
(Erector Spinae) and
Transversospinal Groups
•Each group comprised of 3
major subgroups, also with
regional specializations
Splenius Muscles
•Relationship of trapezius to splenius: Atlas, 12th ed. Fig 4.29, p.
308
•Distinctive fiber direction: diagonally upward and laterally
•Splenius Capitis is superior, and inserts into skull
•Splenius Cervicis inserts on cervical transverse processes
•Acting unilaterally, both muscles rotate face to same side; left
and right act together to extend neck
Erector Spinae
•Origin: sacrum, iliac
crest, vertebral
spines
•3 columns
•Iliocostalis
(lateral) inserts on
ribs
•Longissimus
(middle column)
inserts on
transverse
processes
•Spinalis: (medial
column) inserts
on spines of
vertebrae
Transversospinalis
Group
Rotate body to
opposite side
Semispinalis muscle
Fig. 4.32
Grant’s Atlas
Multifidus
•Semispinalis is
absent in the
lumbar region.
•Multifidus is
prominent in
lumbar region
•Anterior and
posterior layers of
lumbar fascia
form compartment
around erector
spinae (removed)
and
transversospinal
muscles.
Rotatores brevis
Rotatores longus
Fig. 4.34
Grant’s Atlas
Suboccipital Region
•2 rectus, 2
oblique muscles
•C1 motor to the
4 muscles
•C2 cutaneous
(the Greater
Occipital nerve)
•Splenius &
semispinalis
capitis = roof
•Semispinalis
cervicis ends at
C2 spine
•Vertebral artery
supplies brain
1
Meninges: 3 layers covering CNS
From Outside
in:
•Epidural
Space
•Dura (tough)
•Subdural
Space
•Arachnoid
(spidery)
•Subarachnoid
Space (CSF)
•Pia (tender)
Dura Mater
Tube of tough collagenous
tissue that covers cord and
cauda equina
Continuous with dura of brain
and extends to S2 vertebra
Below S2 the dura is reduced
to a slender strand which
connects to the coccyx.
THE SUBARACHNOID SPACE
ENDS HERE.
Dural sleeves extend out
around the spinal nerves to
blend with the perineurium on
the peripheral nerves
Arachnoid Mater (spidery mother)
Middle layer of meninges
Smooth where it contacts
dura
Thin, filmy, spider-web like
extensions attach to pia
Bounds the subarachnoid
space which contains
cerebrospinal fluid
Pia Mater (tender mother)
•Innermost covering of cord
•Closely bound to cord and
nerve rootlets as they cross
the subarachnoid space
•Denticulate ligaments are
specializations of pia which
anchor the spinal cord
laterally to the dura, and is
most important to preventing
lateral and AP displacement of
the spinal cord
•Dorsal and ventral rootlets
pass on dorsal and ventral
sides, respectively.
Ventral
Rootlets
Fig. 4.43A
Grant’s Atlas
Conus medullaris
Filum terminale
internum
Cauda equina
Fig. 4.43A
Grant’s Atlas
12th ed.
Dura mater
Filum terminale
externum
Fig. 4.42
Grant’s Atlas
Filum terminale
internum (Pia)
Filum terminale
Fig. 4.43C
Grant’s Atlas
Epidural Space Contains
the Internal Vertebral Plexus
•Internal venous
plexus is within
vertebral canal, in
the epidural space
•External plexus is
outside vertebral
canal
•Longitudinal
vessels can spread
disease from
pelvis to cranium
•Segmental veins
exit at each level
Spinal Cord
•Spinal cord is initially
the same length as the
vertebral column
•One pair of spinal
nerves exits at each
vertebral level
•Growth of vertebrae
outpaces that of cord
•Adult cord ends at L2
• Cord segments located
higher than vertebra
where nerves exit: S1S5 segments are at L1-l2
vertebrae; Lumbar
segements are at T 11,
T12 & L1
Embryo
Adult
C1
C1 vertebra
C8
T1 vertebra
T1 nerve
L1
Fig.
4.48
Grants
Atlas,
12th
ed.
L1
S1
S1
Herniated Nucleus Pulposus
Clinical Rule: A protruded
nucleus pulposus, when small,
will usually affect the spinal
nerve whose number
corresponds to the number of
the vertebra below the disk.
Posterior Longitudinal
Ligament
•Located
Posterior to the
vertebral bodies
•Located
Anterior to the
spinal cord
•Resists Flexion
of the spine
(bending
forward)
Herneated disks in the
cervical region follow the
same rule, but for a
different reason.
---One exception---
Other forms of encroachment
on nerve roots
1. Arthritic enlargement of facet joints
2. Bony projections from traumatic or
arthritic reactions with the interbody joints
(of Luschka) which then encroach upon
anterior parts of the cervical foramina.
3. Fractures or dislocations at any vertebral
level
Today’s Dissection
• Even numbered tables: Deep Back, and
once-over on Suboccipital Region
• Odd numbered tables: Laminectomy and
spinal cord T6- L5
– Clear out deep back muscles bilaterally
– Saw through laminae; angle saw to
enter spinal canal, with as wide an
opening as possible
– Observe structures inside the vertebral
canal: meninges, nerve rootlets, etc.