Download 03. SPINAL CORD (EXTERNAL FEATURES and blood











Beginning:
At the foramen magnum as a
continuation of
the
Medulla Oblongata of the
brain.
Shape:
Cylindrical.
Length:
About (45) cm.
Occupies:
Upper 2/3 of the vertebral
(spinal) canal of the vertebral
column.




(1) Up till the 3rd month of
Fetal Life:
The spinal cord occupies the
Entire Length of the
vertebral canal.
(2) At birth :
It terminates at the level of
L3.




(3) Children :
It ends at the Upper
Border of the 3rd
Lumbar vertebra.
(4) Adults :
It terminates at the
Intervertebral disc (1st2nd ) Lumbar vertebrae.
Cervical:
(C3- T1) Segments.

For the Brachial
Plexus.
Lumbar:
(L1- S3) Segments.

For the

Lumbar and Sacral
Plexuses.






Conus Medullaris:
A conical termination
Caudal to the Lumbar
Enlargement.
FilumTerminale:
A filament of connective
tissue arises from the tip
of the conus.
It is attached to the 1st
Coccygeal Vertebra.





Anterior:
Deep Anterior
(Ventral)
Median Fissure.
Posterior:
Shallow Posterior
Median Sulcus.



The Spinal Cord
receives
Information from
and Controls the
Movement of the
Trunk and Limbs.
It has (31) paired
Spinal Nerves.


Two linear series (6-8) of
Nerve Fascicles are
attached to the
Dorsolateral and
Ventrolateral aspects of
the cord.
The Fascicles coalesce to
form Dorsal and Ventral
Nerve Roots.


The Roots pass to
their corresponding
Inter vertebral
Foramena.
Near which they
join to form the
Spinal Nerve
Proper.



Carry:
Primary Afferent
Neurons from the
peripheral sensory
receptors to the
spinal cord and brain
stem.
Their cell bodies are
in the Dorsal Root
Ganglia.




Carry :
1.Efferent neurons
(Lower Motor Neurons)
Their cell bodies are
located in the Spinal
Gray matter.
2.Preganglionic
Autonomic neurons.





Spinal Nerves are
Mixed.
Contain:
Both Afferent and
Efferent fibers.
Each spinal nerve is
divided into
Dorsal and Ventral
Rami.







Dorsal Ramus :
Thin.
Supplies muscles and skin
of the back.
Ventral Ramus :
Larger.
Supplies muscles and skin
of the Front of the body
and limbs.
Connected to the
Sympathetic Chain by the



The spinal cord is
Segmented.
In the Living
The approximate level of
the segments is
identified by the
Posterior Spinous
Process of the vertebrae.







Cervical Segments:
One spine Higher than their
corresponding vertebrae.
C7 Segment is adjacent to
C6 Vertebra.
Thoracic segments :
Two spines Higher .
Lumbar segments :
Three- Four spines Higher.


Cervical Region :
Cervical segments lie
adjacent to their
corresponding Vertebral
Bodies.



1-7 C : Above the
Upper Seven
Cervical Vertebrae.
C8 : Below 7th
Cervical Vertebra.
T1 and the rest of
the nerves: Below
their Corresponding
Vertebrae.


The Lumbar and Sacral
nerves take an Oblique
Course to reach the
intervertebral
foramina.
The resulting leash of
nerve roots forms the
Cauda Equina.





Pia Mater
The inner most layer.
A delicate ,vascular
membrane.
It is Closely applied to
the surface of the
spinal cord.
It extends inferiorly as
the Filum Terminale.





A flat membrane formed
from Pia Mater.
Extension:
Along a midway line
between the dorsal and
ventral nerve roots.
Laterally to adhere to
the Arachnoid and Dura.
The spinal cord is
suspended in the middle
of the dural sheath.







Arachnoid:
A a fibrous membrane.
It Loosely covers the
spinal cord.
Dura:
A dense, strong fibrous
membrane.
It is continuous
superiorly with the
Meningeal layer of the
Cranial Dura.



They extend along
Each Nerve Root and
become continuous
with its Epineurium.
Inferiorly
They extend to the
2nd sacral vertebra.






Epidural
Separates Dural Sheath from
the Vertebral Canal.
Contains the Internal
Vertebral Venous Plexus.
Subdural
A thin space.
Separates Dura from
Arachnoid.




Subarachnoid
Contains Cerebro
Spinal Fluid.
Terminates
At the level of S2




Held in position by :
Laterally : Denticulate
Ligament.
Inferiorly : Filum
Terminale.
The spinal cord is
Cushioned against
Trauma by:
Cerebrospinal Fluid.






Site :
Subarachnoid Space
(L2-L3 or L3 –L4).
Not Allowed in Children.
Indications:
1. Diagnostic purposes.
2. Radiological study
(Myelography).

Injection of
Anaesthetics into
the Epidural Space
It is for Surgical
Procedures as in
Labour.



1. Anterior spinal
artery.
2. Posterior
spinal Arteries.
3. Radicular
Arteries.
A single Y shaped artery.
Arises from :Vertebral artery
at the level of the medulla.
 Supplies the cord at the
Cervical Level.
 It is most vulnerable in the
anterior part of the cord
particularly in the Thoracic
Segment.
 Its Occlusion causes Acute
Thoracic Syndrome with
Paraplegia and
Incontinence.





Two arteries.
Arise from
. Vertebral Or
Posterior Inferior
Cerebellar arteries.
Spinal Arteries (Anterior
&Posterior) are
Insufficient alone to
supply the cord Below
the Cervical Level.





Origin from following
arteries :
1. Ascending cervical
2. Intercostal.
3. Lumbar.
They share in the
arterial supply of the
cord Below the Cervical
Level.
They Anastomose freely
with the Spinal
Arteries.






Artery of Adamkiewicz.
It may arise from:
Intercostal or Lumbar
arteries.
It supplies
Lower half of the spinal
cord (T8 –L3).
These are Vulnerable
Segments.
Occlusion of the artery
may cause Muscle
weakness and Paralysis.






Six Longitudinal
Interconnecting Venous
Channels.
(1) Anterior and Posterior
Spinal veins in the midline.
(2) Anterolateral and
Posterolateral paired veins
situated near the lines of
attachment of the
Ventral and
Dorsal roots.
(3) Anterior and Posterior
Radicular Veins.



(4) Internal
vertebral venous
plexus in the
Epidural Space.
(5) External
Vertebral Venous
Plexus.
(6) Ascending
Lumbar, Azygos and
Hemiazygos Veins.






The spinal nerve roots can be
injured by Compression of
Prolapsed Intervertebral Discs
It is manifested by:
1. Paraesthesia (tingling
sensations).
2. Weakness and wasting of
the muscles.
3. Numbness of the skin
corresponding to the
dermatomal distribution.
4. Loss of Tendon Reflexes.






(A) Cervical
Pain in the neck radiating to
the arm and hand.
(B) Lumbar
1. Back pain.
2. Sciatica ( radiation of
pain into the legs) .
A large Lumbosacral
prolapsed disc can cause
paralysis of the bladder and
incontinence.