Anatomy of the
Spinal Cord
(Lecture 1)
LECTURER
PROF. DR. ALI K. AL-SHALCHY
MBCHB/ FIBMS/ MRCS/ FRCS
2017
Definition
THE SPINAL CORD IS THE
CYLINDRICAL
BUNDLE
OF
NERVE
FIBERS
AND
ASSOCIATED TISSUE WHICH
IS ENCLOSED IN THE SPINE
AND CONNECTS NEARLY ALL
PARTS OF THE BODY TO THE
BRAIN AND VICE VERSA. THE
SPINAL
CORD
WITH
THE
BRAIN FORMS THE CENTRAL
NERVOUS SYSTEM.
THE
SPINAL
CORD
EXTENDS
FROM
FORAMEN
MAGNUM
TO
L1
OR
L2
LEVELS IN ADULTS OR L5 IN
PEDIATRIC AGE GROUP.
THE SPINAL COLUMN IS THE SERIES OF
ARTICULATED
VERTEBRAE,
SEPARATED
BY
INTERVERTEBRAL DISKS AND HELD TOGETHER
BY MUSCLES AND TENDONS, THAT EXTENDS
FROM
THE
CRANIUM
TO
THE
COCCYX
,
ENCASING THE SPINAL CORD AND FORMING
THE SUPPORTING AXIS OF THE BODY; THE
SPINE.
IT CONSISTS OF 33 VERTEBRAE IN THE
VERTEBRAL
COLUMN,
IF
ASSUMING
4
COCCYGEAL VERTEBRAE. THE ARTICULATING
VERTEBRAE ARE NAMED ACCORDING TO THEIR
REGION OF THE SPINE. THERE ARE 7 CERVICAL
VERTEBRAE, 12 THORACIC VERTEBRAE AND 5
LUMBAR VERTEBRAE. ALL THE ARTICULATING
VERTEBRAE
ARE ESSENTIALLY ALIKE BUT
THERE
ARE
SOME
VARIATIONS
BETWEEN
THOSE IN DIFFERENT REGIONS.
ALSO CALLED THE VERTEBRAL COLUMN.
Regions of the Spinal Cord
THE
SPINAL
CORD
IS
DIVIDED
INTO
FOUR
DIFFERENT
REGIONS:
THE
CERVICAL,
THORACIC,
LUMBAR
AND
SACRAL
REGIONS
.
THE
DIFFERENT
CORD
REGIONS
CAN
BE
VISUALLY
DISTINGUISHED
FROM ONE ANOTHER.
TWO
ENLARGEMENTS
OF
THE SPINAL CORD CAN BE
VISUALIZED:
THE
CERVICAL
ENLARGEMENT,
AND
THE
LUMBAR ENLARGEMENT.
Segmental and Longitudinal Organization of
the Spinal cord
THE
CORD
IS
SEGMENTALLY
ORGANIZED.
THERE
ARE
31
SEGMENTS, DEFINED BY 31 PAIRS OF
NERVES EXITING THE CORD. THESE
NERVES
ARE
DIVIDED
INTO
8
CERVICAL,
12
THORACIC,
5
LUMBAR,
5
SACRAL,
AND
1
COCCYGEAL NERVE .
DORSAL AND VENTRAL ROOTS
ENTER AND LEAVE THE VERTEBRAL
COLUMN RESPECTIVELY THROUGH
INTERVERTEBRAL FORAMEN AT THE
VERTEBRAL
SEGMENTS
CORRESPONDING TO THE SPINAL
SEGMENT.
Localization of the Spinal Segments and
Nerves
BECAUSE THE SPINAL CORD IS SHORTER THAN THE VERTEBRAL
COLUMN, VERTEBRAL AND SPINAL CORD SEGMENTAL LEVELS ARE
NOT NECESSARILY THE SAME. THE C1 THROUGH C8 SPINAL CORD
SEGMENTS LIE BETWEEN THE C1 THROUGH C7 VERTEBRAL
LEVELS. THE T1 THROUGH T12 CORD SEGMENTS LIE BETWEEN T1
THROUGH T8. THE FIVE LUMBAR CORD SEGMENTS ARE SITUATED
AT THE T9 THROUGH T11 VERTEBRAL LEVELS, AND THE S1
THROUGH S5 SEGMENTS LIE BETWEEN T12 TO L1. THE C1
THROUGH C7 NERVE ROOTS EMERGE ABOVE THEIR RESPECTIVE
VERTEBRAE; THE C8 NERVE ROOT EMERGES BETWEEN THE C7 AND
T1 VERTEBRAL BODIES. THE REMAINING NERVE ROOTS EMERGE
BELOW THEIR RESPECTIVE VERTEBRAE.
THE SPINAL NERVES WHICH LEAVE THE SPINAL CORD ARE
NUMBERED ACCORDING TO THE VERTEBRA AT WHICH THEY EXIT
THE SPINAL COLUMN. SO, THE SPINAL NERVE T4, EXITS THE
SPINAL COLUMN THROUGH THE FORAMEN IN THE 4TH THORACIC
VERTEBRA.
IN THE CERVICAL REGION
OF THE SPINAL CORD, THE
SPINAL NERVES EXIT ABOVE
THE VERTEBRAE. A CHANGE
OCCURS
WITH
THE
C7
VERTEBRA HOWEVER, WHERE
THE C8 SPINAL NERVE EXITS
THE VERTEBRA BELOW THE C7
VERTEBRA.
THEREFORE,
THERE IS AN 8TH CERVICAL
SPINAL NERVE EVEN THOUGH
THERE IS NO 8TH CERVICAL
VERTEBRA.
FROM
THE
1ST
THORACIC
VERTEBRA
DOWNWARDS,
ALL
SPINAL
NERVES EXIT BELOW THEIR
EQUIVALENT
NUMBERED
VERTEBRAE.
8
REGIONS
SPINAL
SEGMENTS
VERTEBRAL
LEVEL
GENERAL
RULE
Upper
cervical
C1
C1
Same level
Lower
cervical
C6
C5
One
vertebra
above
Upper
thoracic
T5
T3
Two
above
Lower
thoracic
T10
T7
Three above
lumbar
L1 TO L5
T10 TO T11
Three to five
above
Sacral and
coccygeal
S1 TO S5
C X 1
T12 TO L1
Six to ten
above
Anatomy of the Vertebra
A
TYPICAL
VERTEBRA
CONSISTS OF TWO ESSENTIAL
PARTS: AN ANTERIOR (FRONT)
SEGMENT,
WHICH
IS
THE
VERTEBRAL
BODY;
AND
A
POSTERIOR
PART
–
THE
VERTEBRAL (NEURAL) ARCH –
WHICH
ENCLOSES
THE
VERTEBRAL
FORAMEN.
THE
VERTEBRAL ARCH IS FORMED
BY A PAIR OF PEDICLES AND A
PAIR
OF
LAMINAE,
AND
SUPPORTS
SEVEN
PROCESSES,
FOUR ARTICULAR(2 SUPERIOR
AND
2
INFERIOR),
TWO
TRANSVERSE,
AND
ONE
SPINOUS,
THE
LATTER
ALSO
BEING KNOWN AS THE NEURAL
SPINE.
Anatomy of C1 Vertebra (The Atlas)
HAS NO VERTEBRAL BODY.
CONSISTS OF AN ANTERIOR RING AND
POSTERIOR ARCH.
BILATERALLY
CONCAVE
SUPERIOR
ARTICULAR SURFACES ARTICULATE WITH
THE OCCIPITAL BONE.
AT THE POSTERIOR MIDLINE THE TWO
PARTS OF THE ARCH FORM THE POSTERIOR
TUBERCLE.
THE ANTERIOR RING HAS AN ANTERIOR
PROMINENCE (ANTERIOR TUBERCLE).
ON THE POSTERIOR LATERAL ARCH,
BEHIND THE POSTERIOR ASPECT OF THE
SUPERIOR ARTICULAR SURFACE A SHARP
RIM MARKS THE SULCUS ARTERIOSUS
WERE THE VERTEBRAL ARTERY RUNS
BEFORE ENTERING THE SUBARACHNOID
SPACE OF THE SKULL VIA THE ATLANTO-
OCCIPITAL MEMBRANE.
Anatomy of C2 (The Axis)
THE
ODONTOID
PROCESS
(DENS) IS THE MOST PROMINENT
FEATURE
OF
C2
AND
CONSTITUTES
THE
SUPERIOR
PROJECTION
FROM
THE
VERTEBRAL
BODY
ARTICULATING
WITH
THE
ANTERIOR
RING
OF
C1
ANTERIORLY AND TRANSVERSE
LIGAMENT POSTERIORLY.
THE TRANSVERSE FORAMEN IS
LOCATED ANTEROLATERAL TO
THE PEDICLE AND IS PARTIALLY
COVERED
BY
THE
SUPERIOR
FACET
MEDIALLY.
IT
REPRESENTS THE PATHWAY OF
Curves of The Vertebral Column
WHEN VIEWED FROM THE SIDE
(SAGITTAL
PLANE)
THE
MATURE
VERTEBRAL COLUMN HAS 4 DISTINCT
CURVES.
THESE
CURVES
ARE
DESCRIBED
AS
BEING
EITHER
KYPHOTIC OR LORDOTIC.
A KYPHOTIC CURVE IS A CONVEX
CURVE IN THE SPINE (I.E. CONVEXITY
TOWARDS THE BACK OF THE SPINE).
THE CURVES IN THE THORACIC AND
SACRAL SPINE ARE KYPHOTIC.
A LORDOTIC CURVE IS CONCAVE
(I.E. CONCAVITY TOWARDS THE BACK
OF THE SPINE), AND IS FOUND IN THE
CERVICAL AND LUMBAR LEVELS OF
THE SPINE.
BLOOD SUPPLY OF THE
SPINAL CORD
EXTRASPINAL
SEGMENTAL ARTERIES
INTRASPINAL
ANTERIOR SPINAL ARTERY from the vertebral a.
POSTERIOR SPINAL ARTERIES from vertebral a. or PICA.
RADICULAR ARTEIES from the Aorta
INTRAMEDULLARY ARTERIES
ANT RADICULAR
SEGMENTAL ARTERIES
POST RADICULAR
12 ant radicular
contribute to pia plexus
14 post radicular
join the
ANT SPINAL A
join the
POST SPINAL A
sulcal branches
Largest radicular a
In upper lumbar region
(ADAMKIEWICZ)
small plexuses present in pia
VASORORONA
supply
remainder of dorsal gray horns
Supply
Ventral gray horns
Part of dorsal gray horns
supply white matter beneath pia
dorsal funiculi of white matter
Ventral and lat white funiculi
Live operative picture of radicular artery
Note the small size in relation to the spinal nerve
Intraop photograph noting the artery of Adamkiewicz
Thank you