Transcript Gross Anatomy: Spinal Cord and Meninges

Gross Anatomy:
Spinal Cord and Meninges
Spinal Cord
The spinal cord:
• occupies the vertebral canal
• in infants the spinal cord extends into
the sacrum
• in the adult the cord extends from the
cranial border of the atlas to L2
• level of termination is slightly more
superior in flexion
Spinal Cord
The spinal cord is:
• part of the central nervous system.
• segmental in nature
What is a spinal cord segment?
How many segments are there?
Note the relationship of the “nerves” to
the spinal cord:
Dermatomes, Myotomes and Sclerotomes
C5
C6
C7
Teres Minor
Supraspinatus
Rhomboids
Infraspinatus
Deltoid
Teres Major
Biceps
Brachialis
Serratus Anterior
Subscapularis
Pectoralis Major
Pectoralis Minor
Coracobrachialis
Latissimus Dorsi
Anconeus
Triceps
C8
T1
Spinal Cord Enlargements
Cervical Enlargement
• the larger and more pronounced of the
enlargements
• extends from about C3 to T2
Lumbar Enlargement
• extends from L1 to S3
Below the lumbar enlargement, the cord
tapers to the conus medullaris.
“The Heavenly Seven”
Nerve Roots
Nerve Roots and IV Discs
A 18-year-old female presents with pain
in her neck and in her right arm.
Physical exam reveals pain along the
lateral arm, involving the thumb. Grip
strength is normal. Her upper limb
reflexes on the right side are:
• biceps = 1/4
• brachioradialis = 0/4
• triceps = 2/4
What is the most likely etiology for
these findings?
CLINICAL CONCEPT
Muscle Strength is measured on a
scale of 0 to 5.
> Normal strength is 5/5
> Paralysis is 0/5
Muscle Stretch Reflexes are measure
on a scale of 0 to 4.
> Normal is 2/4
> PNS lesions are 0 or 1/4
> CNS lesions are 3 or 4/4
Note the position of SPINAL CORD SEGMENTS relative to VERTEBRAL BODIES!
Student Dr. Spencer?
A compression fracture of the L2
vertebral body would most directly
affect what level of the SPINAL
CORD?
A. T12
B. L1
C. L2
D. L4
E. Cx1
Blood Supply to the Spinal Cord
• Branches from the Vertebral Artery - Anterior and Posterior
Spinal Arteries
• Segmental Spinal Arteries
– anterior radicular
– posterior radicular
– variable segmental medullary arteries
Blood Supply to the
Spinal Cord
Venous Drainage of the Spinal
Cord
Intervertebral veins: follow arteries
and nerves. They are draining spinal
veins
Spinal Veins:
Internal Venous Plexus: communicates
with the external spinal venous
plexus
Venous Drainage of the
Vertebral Column
External Spinal Venous Plexus:
Basivertebral Veins: they drain the
vertebral bodies
A 66-year-old male presents with the chief complaint of
increased urinary frequency, back pain, lower limb weakness
and numbness of two weeks duration. A digital rectal exam
suggests prostate cancer. A gadolinium-enhanced MRI of
the spine reveals:
Think/Pair/Share
A 12-year-old male presents with the chief complaint of fever, headaches,
nuchal rigidity, nausea and lethargy of two days duration. History and
physical exam leads to the suspicion of meningitis.
You need to sample cerebrospinal fluid. Where is it?
What layers do you need to go through to sample CSF?
Where should you stick your needle?
Spinal Meninges
The spinal cord (in fact the entire CNS) is
enclosed in three layers of tissue, the
meninges.
The meninges are from external to internal:
1. Dura mater
2. Arachnoid mater
3. Pia mater
Spinal Meninges
The dura mater:
• is the outermost covering
of the spinal cord
• is a thick and dense
inelastic membrane
• is attached around the
foramen magnum and
bodies of the 2nd and 3rd
cervical vertebrae
• has tubular extensions for
the roots of the spinal
nerve as they pass
thorough the IV foramen
Spinal Meninges
The epidural space:
• is between the dura and
the periostium of the
vertebrae
• extends to the skull - fluids
put into the sacral hiatus
can spread to the base of
the skull
The subdural space:
• is a potential space
between dura and the
arachnoid that contains
only a serous fluid
• ends at the level of S2
Potential spaces can become REAL spaces when they fill with blood, air, etc.
Spinal Meninges
The arachnoid is a delicate membrane, that is
separated from the dura by a potential
subdural space. The arachnoid is not attached
to the dura, but held to it by the normal
pressure of CSF
The subarachnoid space:
• is between the arachnoid and the pia
• contains cerebrospinal fluid (CSF), blood
vessels and connective tissue
• surrounds the cord and spinal nerves, ends at
the level of S2
Spinal Meninges
The arachnoid is only loosely related to the underlying
pia mater.
• the spinal cord ends at L2
• the dural sac and arachnoid end at S2
As a result there is a large space between the
arachnoid and pia in the lumbar region:
Lumbar Cistern:
Sampling CSF:
Lumbar puncture and intracranial pressure:What about a newborn?
Lumbar Cistern
Lumbar Puncture
Spinal Meninges
The pia mater:
• faithfully invests the spinal cord and
brain
• is a vascular membrane (holds all the
vessels like posterior and anterior spinal
artery)
Spinal Meninges
Denticulate ligaments:
• continuous with the pia on the cord,
between the dorsal and ventral roots
• tooth-like process, 21 in number, stops
at the T12 level
• serves to stabilize the cord within the
dura
Spinal Meninges
The filum terminale:
• is a fine filament of pia and
connective tissue that
descends from the conus
medullaris
• descends to the level of S2
where it is joined by dura
(filum terminale internum)
• descends to coccygeal levels
and anchors the spinal cord in
the dura sac (filum terminale
externum)
Spinal Meninges
Spinal block:
Epidural block: injecting
anesthesia outside the dura