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Week 27
Clinical Anatomy of the Vertebral Canal, Spinal cord and Spinal nerves
Understand the concepts & associated principles, functional and clinical applications
of the topographical anatomy of the vertebral canal, spinal cord and spinal nerves
Vertebral Column
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extends from the skull to the apex (tip) of coccyx and forms the skeleton of the neck,
back and the main part of the axial skeleton (the articulated bones of the skull, vertebral
column, ribs and sternum)
72-15cm long in adults and ¼ is formed by the fibrocartilaginous intervertebral (IV) discs
that separate and bind the vertebra
functions:
o protects the spinal cord and spinal nerves
o supports the weight of the body
o provides partly rigid and flexible axis for the body and a pivot for the head
o plays an important role in posture and locomotion
consists of 33 vertebrae in 5 regions:
o 7 cervical
o 12 thoracic
o 5 lumbar
o 5 sacral
o 4 coccygeal
motion only occurs between the 24 cervical, thoracic and lumbar vertebrae
the 5 sacral vertebrae are fused to form the sacrum and the 4 coccygeal are fused to
form the coccyx
flexible because consists of many small bones separated by resilient IV discs
Curvatures
 1° = thoracic and sacral curvatures develop during foetal period
 2° = cervical and lumbar curvatures begin developing in foetal period but do not become
obvious until infancy (with holdingthe head up and walking)
Abnormal curvatures
 Kyphosis – (hunchback/humpback) abnormal ↑ of thoracic curvature
 Lordosis – (hollow back/sway back) anterior rotation of the pelvisat hip joint
producing ↑lumbar curvature
 Scoliosis – (crooked or curved back) abnormal lateral curvature
Vertebrae
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vary in size from one region of the vertebral column to another
a typical vertebra consists of a:
o vertebral body
o vertebral (neural) arch
o seven processes
the vertebral body
o anterior, gives strength to the vertebral column and supports the body weight
the vertebral arch
o posterior to body
o formed by right and left pedicles and laminae
pedicles
o short, stout processes that join vertebral arch to vertebral body
o project posteriorly to meet two broad, flat plates of bone – laminae
vertebral foramen
o formed by vertebral arch and posterior wall of vertebral body
vertebral canal
o succession of vertebral foramina in the articulated column
o contains spinal cord, meninges, fat, spinal nerve roots and vessels
vertebral notches
o indentations formed by the projection of the body and articular processes
above and below the pedicle
o superior an inferior notches of adjacent vertebrae contribute to the IV foramina
IV Foramina
o passage for spinal nerves roots and accompanying vessels and contain dorsal
root ganglia
7 processes:
o spinous process
– projects posteriorly from vertebral arch at junction of laminae
– overlaps vertebra below
o 2x transverse processes
– project posterolaterally from junctions of pedicles and laminae
o 4x articulate processes
– 2x superior and 2x inferior
– also arise from junctions of pedicles and laminae
– are in apposition with the corresponding vertebrae superior and inferior
to them and restrict movement in certain directions
Regional Characteristics of the Vertebrae
Cervical
– distinctive feature is oval foramen of transverse process (for passage of the vertebral artery)
– C3-C7 – large vertebral foramina due to cervical enlargement of the spinal cord
– C3-C6 – short spinous processes
– C7 – long spinous processes, therefore this vertebra is called the vertebra prominens
– C1 and C2 are atypical
Atlas (C1)
– widest of the cervical vertebrae and supports the skull
– kidney-shaped, concave superior articular surfaces receive the two large protuberances at
the sides of the foramen magnum, the occipital condyles
– no spinous process or body
Axis (C2)
– strongest of the cervical vertebrae because C1 rotates on it
– has two large superior articular surfaces on which the atlas rotates
– dens (odontoid process) is distinguishing feature which projects superiorly
– dens is held in place by the transverse ligament of the atlas which prevents horizontal
displacement of the atlas
– has large bifid spinous process that can be felt deep in the nuchal groove
Thoracic
– characteristic features are costal facets for articulation with ribs
– one facet on each side of the vertebral body (articulation with head of rib) and one on each
transverse process of T1-T10 (for tubercle of rib)
– spinous processes are long and slender and middle ones are directed inferiorly over
vertebral arch of vertebra below
– T1 is atypical in that it has an entire costal facet for the 1st rib superiorly and a demifacet
that contributes to the articular surface for the 2nd rib inferiorly; and has a long, almost
horizontal spinous process
Lumbar
 massive kidney-shaped body when viewed anteriorly
 triangular vertebral foramen
 long and slender transverse processes with accessory process on posterior surface of
base of each process
 short, sturdy and thick spinous processes
 L5 is largest of all movable vertebrae and carries the weight of the whole upper body
 transverse processes project posterosuperiorly as well as laterally – on the posterior
surface of the base of each one is an accessory process (attachment for medial
intertransverse lumborum muscle)
 on the posterior surface of the superior articular process is the mamillary process
(attachment for multifidus and medial intertransverse muscles)
Sacrum
 Consists of five fused vertebrae (fuse shortly after puberty)
 curved with a convex posterior surface.
 narrow inferior portion is called the apex and the broad superior region is called the
base
Coccyx
 small most inferior vertebrae consisting of 3-4 fused vertebrae
 acts as a site of muscle and ligament attachment
Spinal Cord and meninges
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located in the vertebral canal formed by successive vertebral foramina
Spinal cord:
o cylindrical and slightly flattened anteriorly and posteriorly
o protected by spinal cord and its ligaments and muscles, the meninges and CSF
o begins as continuation of the medulla oblongata, the caudal part of the
brainstem
o adults: extends from foramen magnum to tapering end (medullary cone) at L2
(usually)
o enlarged in 2 regions for innervation of the limbs:
 Cervical enlargement (C4-T1): most ventral rami of the spinal nerves
arising from it form the brachial plexus of nerves that innervates the
upper limbs
 Lumbosacral enlargement (T11-L1): ventral rami make up the lumbar
and sacral plexuses that innervate the lower limbs
o cauda equina – the bundle of spinal nerve roots running through the lumbar
cistern (subarachnoid space) and consists of spinal nerve roots arising from the
lumbosacral enlargement and the medullary cone
Spinal Meninges:
 Dura Mater:
o outermost, tough fibrous and elastic
o separated from the vertebrae by the extradural or epidural space that contains
adipose tissue and a venous plexus
o forms the dural sac – long tubular sheath within the vertebral canal that
adheres to margin of foramen magnum of skull where it is continuous with te
dura mater of the brain
o pierced by spinal nerves and anchored inferiorly to the coccy by the terminal
filum
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Arachnoid mater:
o delicate, avascular membrane of fibrous and elastic tissue
o lines dural sac and encloses CSF-filled subarachnoid space containing spinal
cord, spinal nerve roots and spinal ganglia
o not attached to dura but held against it by pressure of CSF
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Pia mater:
o innermost covering membrane of the spinal cord and also covers
o consists of flattened cells
o separated from arachnoid by subarachnoid space containing CSF
Spinal Nerves
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31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
several rootlets emerge from the dorsal and ventral surfaces of the spinal cord and
converge to form the dorsal and ventral roots of the spinal nerves
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Dorsal roots of spinal nerves contain sensory afferent fibres from skin, subcutaneous
and deep tissues and viscera
Ventral Roots of spinal nerves contain motor/efferent fibres to skeletal muscle and may
contain presynaptic autonomic fibres
Ventral Gray horns of spinal cord – made up of the cell bodies of axons of ventral roots
Spinal/Dorsal root ganglia – cell bodies of axons making up the dorsal roots (outside the
spinal cord)
dorsal and ventral nerve roots unite at their points of exit from the vertebral canal to
form a spinal nerve
each spinal nerve then divides almost immediately to form a dorsal 1° ramus (supply
skin and muscle of the back)and a ventral 1° ramus (supply limbs and rest of trunk)