The document provides an overview of the neuroanatomy of the spinal cord. It discusses the coverings of the spinal cord including the dura mater, arachnoid mater, and pia mater. It describes the internal structure of the spinal cord including the grey matter consisting of the anterior, posterior, and lateral grey columns, and the white matter consisting of the anterior, posterior, and lateral funiculi. It also discusses the enlargements of the spinal cord, spinal nerves, spinal segments, cauda equina, and conus medullaris. Additionally, it outlines the different neuronal cells found in the spinal cord grey matter including motor and sensory neurons, and describes the monosynaptic reflex and motor end plate.

1. NEUROANATOMY OF SPINAL CORD
BY
DR SAI PRIYANKA NERUSU (PT)

2. CONTENTS
• INTRO OF SPINAL CORD
• COVERINGS OF SPINAL
CORD
• INTERNAL STRUCTURE
OF SPINAL CORD
• GREY MATTER
• WHITE MATTER
• ENLARGEMENTS OF
SPINAL CORD & IMP
• SPINAL NERVES &
SPINAL SEGMENTS
• CAUDA EQUINA
• CONUS MEDULARIS
• DIFFERENT NEURONAL
CELLS OF SC
• MONOSYNAPTIC
REFLEX
• MOTOR END PLATE
• MOTOR UNIT

3. INTRODUCTION
The spinal cord is the lower elongated
part of the central nervous system (CNS).
It extends as a downward continuation of
medulla oblongata
It starts from the upper border of the
posterior arch of first cervical vertebra
(C1) to the lower border of the first
lumbar vertebra (LI).
Its lower tapering extremity is called conus
medullaris.
The apex of conus medullaris continues
downwards as a thin, thread-like filament
called
Filum terminale.
Spinal cord provides attachment to 31
pairs of spinal nerves which connect it to
the tissues of the trunk, girdles, limbs,
and the viscera.

4. At birth
spinal cord
ends at the
level of third
lumbar
vertebra
while in
adult, it
terminates at
the level of
lower border
of L1 (or the
intervertebra
l disc
between the
LI and L2)

5. SPINAL MENINGES
• The spinal cord is surrounded by three protective membranes called
spinal meninges.
• From outside inwards these are:
Dura Mater,
Arachnoid Mater, And
Pia Mater

7. DURA MATER
The spinal dura extends from foramen
magnum to the lower border of second
sacral vertebra (S2).
The space between spinal dura and
vertebral canal is termed
Epidural space.
The space between dura and arachnoid
mater termed Subdural space.

10. ARACHNOID MEMBRANE
Arachnoid mater is a thin delicate transparent avascular membrane
which invests the spinal cord loosely.
Above it is continuous with the arachnoid mater of the brain and
Below it extends up to the lower border of the second sacral vertebra
(S2).

11. PIA MATER
Pia mater is a thin highly vascular membrane that closely invests the
spinal cord and continues below the spinal cord as a thin thread-like
prolongation, the Filum Terminale.
Subarachnoid space between the pia mater and the arachnoid mater
is filled with cerebrospinal fluid (CSF).
Distal to the termination of spinal cord, the sub-arachnoid space
around the filum terminale, becomes roomy, forming a pool of CSF
called LUMBAR CISTERN.
The lumbar puncture is done at this site to take out the CSF

12. The most distal bulbous part of the spinal cord is called the conus medullaris, and its tapering end
continues as the filum terminale. Distal to this end of the spinal cord is a collection of nerve roots,
which are horsetail-like in appearance and hence called the cauda equina (Latin for horse's tail)

13. SPECIAL PARTS OF PIA MATER
It is a delicate, glistening white thread-like structure extending from
tip of conus medullaris to the first coccygeal vertebra (dorsal aspect).
The filum terminale is mainly composed of non-nervous fibrous
tissue
The filum terminale consists of two parts: (a) filum terminale
internum, and (b) filum terminale externum.
The filum terminale internum lies within the dural sac.
The filum terminale externum lies outside the dural sac, i. e. below
the level of second sacral vertebra

14. GREY MATTER OF SPINAL CORD
The grey matter of the spinal cord forms an H-
shaped mass .
 In each half of the cord the grey matter is
divisible into
o A Larger Ventral Mass, The Anterior (Or Ventral)
Grey Column, And
o A Narrow Elongated Posterior (Or Dorsal) Grey
Column
o In Some Parts Of The Spinal Cord A Small Lateral
Projection Of Grey Matter - Lateral Grey
Column.
The grey matter of the right and left halves of
the spinal cord is connected across the middle
line by the Grey commissure which is traversed by
the central canal.

16. WHITE MATTER OF SPINAL CORD
The white matter of the spinal cord is
divided into right and left halves,
o In Front By A Deep Anterior Median
Fissure, And
oBehind By The Posterior Median
Septum.
 In each half of the cord the white
matter medial to the dorsal grey
column forms the posterior funiculus
(or posterior white column).

17. WHITE MATTER OF SPINAL CORD
The white matter medial and ventral
to the anterior grey column forms
the Anterior Funiculus (Or Anterior
White Column)
while the white matter lateral to the
anterior and posterior grey columns
forms the lateral funiculus.
The white matter of the right and
left halves of the spinal cord is
continuous through the ventral white
commissure which lies anterior to
the grey commissure.

18. GREY MATTER OF SPINAL CORD
The grey matter of spinal cord consists of
(a) nerve cells
(b) neuroglia and
(c) blood vessels.

19. NERVE CELLS :GREY MATTER OF SPINAL CORD
Classification
STRUCTURAL
CLASSIFICATION
GOLGI TYPE 1 GOLGI TYPE II
long axons, which leave
the grey matter Or join
the anterior nerve roots
or form the nerve tracts
short axons, which do not
leave the grey matter
Functional
Classification
Motor Neuron
Present in Anterior
and lateral Horns
Sensory
Neuron
Present in posterior
Horn
InternNeurons
All grey matter od
spinal cord
Alpha
Neurons
Gamma
Neurons
Large Multipolar
cells ,supplies
extrafusal Skeletal
muscle fibers
Small cells ,supply
neuromuscular
spindle
Relay sensory
information to
different parts of the
brain, forming
ascending tracts; or
to the other
segments of spinal
cord forming
interseg-mental
tracts.
connect different types
of neurons, hence also
called association
neurons, can be
excitatory or Inhibitory

20. CELL Groups :GREY MATTER OF SPINAL CORD
Nerve
Groups
Anterior
Grey Column
Posterior
Grey Column
From Apex towards Base
Lateral Grey
Column
Medial Group Central Group Lateral Group
Innervate The Axial
Musculature Of The Neck
And Trunk.
confines in cervical
and lumbosacral
enlargements ,supply
the limb muscle
Forms Three
Definite Nuclei
Substantia
Gelatinosa (of
Rolandi)
nucleus
proprius
nucleus dorsalis
(or Clarke's
column),
visceral afferent
nucleus
• Intermediolateral nucleus extends from T1 to L2
segments of the cord and gives origin to
preganglionic fibres of the sympathetic nervous
system
extends from S2 to S4 segments of the cord
and gives origin to preganglionic fibres of
parasympathetic nervous system (sacral
outflow),

22. LAMINAR ARCHITECTURE OF GREY MATTER (REXED LAMINAE)

23. Types of fibeRs in the white matter
Functionally, the fibres in the white matter of spinal cord are
divided into following three types:
Sensory fibres:
• The central processes of primary sensory neurons of the posterior
root ganglia which enter the spinal cord and ascend or descend for
varying lengths, and
• The ascending fibres from the nuclei of spinal grey columns that
convey sensory modalities to the higher centres.
Motor fibres:
• The descending fibres from higher centres (supraspinal levels) to the
spinal cord, and –
• The nerve fibres of anterior and lateral horn cells that go to the
motor roots of the spinal nerves.
Association fibres:
• These fibres originate and end within the spinal cord,
interconnecting the neurons of the same segment or of different
segmental levels.

24. Types of fibeRs in the white matter
NERVE
FIBERS
MOTOR/
EFFERENT
SOMATIC
EFFERENT
VISCERAL
EFFERENT
SENSORY/
AFFERENT
SOMATIC
AFFERENT
VISCERAL
AFFERENT
Somatic structures are
those present in relation to
the body wall (or soma).
Thus, the skin, bones,
joints and striated muscles
of the limbs and body wall
are classified as somatic.
In contrast, the tissues
that make up the internal
organs like the heart, lungs
or stomach are classified
as visceral. These include
the lining epithelia of
hollow viscera, and
smooth muscle.
General
Visceral
Efferent
Special
Visceral
Efferent
General
Somatic
Afferent
Special
Somatic
Afferent
General
Visceral
Afferent
Special
Visceral
Afferent
Somatic
Efferent

25. General Somatic
Efferent Neuron
supply striated muscle of the limbs and body wall. They also supply the extrinsic
muscles of the eyeballs, and the muscles of the tongue
General visceral Efferent
Neuron
supply smooth muscle and glands. The nerves to glands are called secretomotor
nerves
Special visceral Efferent
Neuron
supply striated muscle developing in branchial arch mesoderm. They are frequently
called branchial efferent or branchiomotor fibres. The muscles supplied include
those of mastication, and of the face, the pharynx and the larynx
General Somatic
Afferent Neuron
(a) sensations of touch, pain and temperature from the skin (exteroceptive
impulses);
(b) (b) proprioceptive impulses arising in muscles, joints and tendons conveying
information regarding movement and position of joints
Special Somatic Afferent
Neuron
carry impulses of: (a) vision, (b) hearing, and (c) equilibrium
General visceral
Afferent Neuron
carry sensations e.g., pain from viscera (visceroceptive sensations)
Special Visceral Afferent
Neuron
sensation of taste
A typical spinal nerve contains fibres of the four general categories. The special
categories are present in cranial nerves only

26. These neurons supply striated muscle.
In the spinal cord the cell bodies of these neurons
lie in the ventral grey column.
They are often referred to as anterior horn cells.
 The neurons are large and multipolar and their Nissl
substance is prominent.
They are designated as alpha neurons to distinguish
them from smaller anterior horn cells called gamma
neurons
The axon of a somatic efferent neuron leaves the spinal
cord through a ventral nerve root to enter the spinal
nerve concerned.
During its course through the spinal nerve (and its
branches) the axon divides into a variable number of
branches each one of which ultimately ends by
supplying one muscle fibre.
SOMATIC EFFERNT NEURONS
The cell bodies of neurons that give
rise to efferent fibres of peripheral
nerves are located within the brain
and spinal cord

27. The region of junction between a terminal branch of the axon and
the muscle fibre has a special structure and is called the motor end
plate or neuromuscular junction.
Depending on the number of branchings one anterior horn cell
supplies a variable number of muscle fibres.
One anterior horn cell and the muscle fibres supplied by it
constitute one motor unit.
In large muscles, where strength of contraction is more important
than precision, a motor unit may contain up to 2000 muscle fibres.
On the other hand in muscles where precision is all important (e.g.,
in muscles of the eyeball) the motor unit may supply as few as six
fibres.
The somatic efferent fibres of cranial nerves are axons of neurons,
the cell bodies of which lie in somatic efferent nuclei in the
brainstem. Their axons pass through the third, fourth and sixth
cranial nerves to supply the extrinsic muscles of the eyeballs; and
through the twelfth cranial nerve to supply muscles of the tongue.
SOMATIC EFFERNT NEURONS

28. These are the neurons that constitute the autonomic
nervous system (sympathetic and parasympathetic).
They supply smooth muscle or glands.
The nerves to glands are called secretomotor nerves.
The pathway for the supply of smooth muscle or gland
always consists of two neurons that synapse in a ganglion.
The first neuron carries the impulse from the CNS to the
ganglion and is, therefore, called the preganglionic neuron.
The second neuron carries the impulse from the ganglion to
smooth muscle or gland and is called the postganglionic
neuron
The cell bodies of preganglionic neurons of the sympathetic
nervous system are located in the lateral grey column of the
spinal cord in the thoracic and upper two lumbar segments
The axons leave the spinal cord through the anterior nerve
roots of spinal nerves and terminate in a sympathetic
ganglion
GENERAL VISCERAL EFFERENT NEURONS

29. The cell bodies of postganglionic neurons are located in sympathetic ganglia
The axons of these postganglionic neurons terminate in relation to smooth muscle in the walls of blood
vessels and in viscera.
They also supply the arrectores pilorum muscles of the skin, and give a secretomotor supply to sweat
glands.
The cell bodies of preganglionic neurons of the parasympathetic nervous system are located in two
different situations.
(a) One group is located in the lateral grey column of the spinal cord in the S2,S3,S4 segments.
• Their axons end in peripheral ganglia (or plexuses) situated in pelvic viscera.
• These ganglia contain the cell bodies of postganglionic neurons.
• The axons of these neurons are short and end by supplying smooth muscle or glands of the viscera
concerned.
(a) The other group of parasympathetic preganglionic neurons is located in the general visceral efferent
nuclei of cranial nerves.
• The axons of these neurons terminate in autonomic ganglia associated with the third, seventh, ninth and
tenth cranial nerves. They supply smooth muscle or glands.
GENERAL VISCERAL EFFERENT NEURONS

30. These are seen only in relation to cranial
nerves.
The cell bodies of these neurons are located
in the branchial efferent nuclei of the
brainstem.
 Their axons pass through the fifth, seventh,
ninth, tenth, and eleventh cranial nerves to
supply striated muscle derived from the
branchial arches.
SPECIAL VISCERAL EFFERNT NEURONS

31. The cell bodies of neurons that give rise to afferent fibres
are located outside the CNS.
In the case of spinal nerves the cell bodies lie in the spinal
ganglia; and in the case of the cranial nerves they lie in
sensory ganglia (e.g., the trigeminal ganglion) associated
with these nerves.
The cells of the dorsal nerve root ganglion are of the
unipolar variety.
 Each cell gives off a single process that divides into a
peripheral process and a central process.
The peripheral process extends into the spinal nerve and
courses through its branches to reach the tissue or organ
supplied.
These peripheral processes are functionally dendrites as
they convey impulses towards the cell body
These peripheral processes constitute the sensory fibres of
peripheral nerves.
AFFERENT NEURONS

32. The sensory impulses brought by these processes from various organs of the body are conveyed to the
spinal cord by the central processes
Within the spinal cord the central processes usually run a short course and terminate by synapsing with
cells in the posterior grey column.
 Some of the central processes enter the posterior funiculus and run upwards to the medulla as ascending
tracts.
AFFERENT NEURONS

33. Spinal Nerves & Spinal Segments
The spinal cord gives attachment, on either side, to a series of spinal
nerves.
Each spinal nerve arises by two roots, anterior (or ventral) and
posterior (or dorsal)
The spinal cord is made up of thirty one segments:
8 cervical
12 thoracic
5 lumbar
5 sacral and
one coccygeal.

36. In subsequent development the spinal cord
does not grow as much as the vertebral
column and its lower end, therefore,
gradually ascends to reach the level of the
third lumbar vertebra at the time of birth,
and to the lower border of the first lumbar
vertebra in the adult
A vertebral spine is always lower than the
corresponding spinal segment.
• In the cervical region there is a
difference of one segment ,
• In the upper thoracic region there is a
difference of two segments and
• In the lower thoracic region there is a
difference of three segments
e.g., the 5th
cervical spine
overlies the 6th
cervical segment
e.g., the 4th
thoracic spine
overlies the 6th
thoracic segment
e.g., the 9th
thoracic spine lies
opposite the 12th
thoracic
segment)

38. Spinal Nerves & Spinal Segments
The rootlets that make up the dorsal
nerve roots are attached to the opposite
tip of the posterior grey column
 The rootlets of the ventral nerve roots
are attached to the anterolateral aspect
of the cord opposite the anterior grey
column.
The ventral and dorsal nerve roots join
each other to form a spinal nerve.
Just proximal to the junction of the two
roots the dorsal root is marked by a
swelling called the Dorsal Nerve Root
ganglion, or spinal ganglion

39. Spinal Nerves & Spinal Segments
The nerve roots of lumbar, sacral and
coccygeal nerves from the caudal part of
the cord takes more or less a vertical course
and form a bunch of nerve fibres around
the filum terminale called cauda equina
because of its fancied resemblance to the
tail of a horse (cauda – tail; equina – horse).
The cauda equina consists of the roots of
the lower four pairs of lumbar, five pairs of
sacral and one pair of coccygeal nerves

41. The posterior horns are connected to the surface by a gelatinous
substance called substantia gelatinosa. The amount of grey matter
and shapes of its horns, and amount of white matter varies at
different levels
• The amount of the grey matter seen at a particular level is well
correlated with the mass of tissue it supplies.
• It is, therefore, maximum in the regions of cervical and lumbar
enlargements, which supply the limbs and their associated
girdles.
• The horns are thus largest in the regions—cervical and lumbar
enlargements.
The amount of white matter in the spinal cord undergoes
progressive increase from below upwards.
1. Progressively more and more ascending fibres are added to the
cord from below upwards.
2. Number of descending fibres decreases in the cord from above
downwards as some of them terminate in each spinal segment.
For this reason, the amount of white matter is massive in the
cervical segments and very less in the sacral segments.

44. REFERNECES
• CLINICAL NEUROANATOMY:SNELL
• TEXT BOOK OF HUMAN NEUROANATOMY:INDERBIR SINGH
• TEXT BOOK OF CLINICAL NEUROANATOMY :VISHRAM SINGH

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