The spinal cord extends from the foramen magnum to the lower border of the first lumbar vertebra. It has 31 pairs of spinal nerves and is divided into cervical, thoracic, lumbar, sacral and coccygeal segments. The spinal cord contains gray matter in an H-shaped arrangement in the center surrounded by white matter. It transmits motor and sensory signals between the brain and body through ascending and descending nerve tracts that contribute to reflexes, voluntary movement and autonomic functions. Injuries or disorders of the spinal cord can impair functions depending on the level and severity of pathology.

1. STRUCTURE OF THE
SPINAL CORD
PRESENTED BY:
RITTIKA DAS NEOGI
M.SC NURSING 1ST YEAR

2. INTRODUCTIO
N
The spinal cord is a vital nervous tissue link
between body and the brain.
It is a part of Central Nervous System (CNS) which
extends caudally.
 It is protected by the bony structure of the vertebral
column.
2 consecutive row of nerve root emerge on each of
its sides & form 31 pairs of spinal nerve.

3. INTRODUCTIO
N
 A specimen of cerebro-spinal fluid is taken by
a procedure called Lumber Puncture.
 A basic knowledge of structure and function
of spinal cord is essential for health care
providers to recognize clinical signs and
symptoms is essential for treatment of patients.

4. FUNCTIONS OF SPINAL CORD
It is the nervous tissue link between the brain and the rest of
the body.
Nerves conveying impulse from the brain to the various
organs and tissue descend through the spinal cord and pass to
the structure they supply.
Sensory nerves from organs and tissue enter and pass
upwards in the spinal cord to the brain.
Some activities of spinal cord are not controlled by brain but
by Spinal Reflexes through extensive neuron network of
sensory and motor neuron.

5. EMBROYOLOGY
After the 3rd week of development, there is
formation of the Neural Tube.
 At about day 28 the brain and the spinal cord is
formed.
 Neuroepithelial cells, which divide and multiply
into neuroblasts and later forms the Gray Mater.
The Ependymal lining of the central spinal canal
cause CSF production.
 Lateral parts forms White Mater.

6. ORIGIN
The spinal cord
extends from Foramen
Magnum, where it is
continuous with the
Medulla Oblongata.

7. TERMINATION
It terminates at the level of the lower
border of the first Lumber Vertebrae and is
anchored distally via the Filum Terminale.
Filam Terminale is the extension of pia
mater that extends from end of spinal cord
to coccyx.
 The spinal cord is 40 – 50 cm long and
1cm – 1.5 cm in diameter.

8. MENINGES
o Dura mater - Thick outermost covering
extending down to the level of the S2Vertebra.
o Arachnoid mater - The middle covering.
o Pia mater - The innermost covering of the spinal
cord. It stabilizes the spinal cord through the
denticulate ligaments, extending till dura mater.

9. SEGMENTS
5 segments
o Cervical
o Thoracic
o Lumbar
o Sacral
o Coccygeal.

10. SEGMENTS
o The spinal cord is incompletely
divided into two, anteriorly by
short shallow Median Fissure and
posteriorly by a deep narrow
septum, Posterior median Septum.
o The cross-section of the spinal
cord shows that it is composed of
grey matter in the center and white
matter in surrounding it supported
by the Neuroglia.

11. SEGMENTS
o The spinal cord is incompletely
divided into two:
o Anteriorly by short shallow
Anterior Median Fissure.
o Posteriorly by a deep narrow
septum Posterior median Septum
or Sulcus.

12. GREY MATTER
 The arrangement in the grey
matter in the spinal cord
resembles the letter H, having
each of:
2 posterior
2 anterior
2 lateral columns.

13. GREY MATTER

14. GREY MATTER
Sensory neuron: receives impulses from periphery of the
body.
Lower motor neuron: transmits impulses to the skeletal
muscles.
Connector neuron: they link sensory and motor neurons at
the same or different levels which form the spinal reflex arc.
The anterolateral columns carry temperature and pain
information.
The dorsal column communicates sense of touch, vibration.
Where nerve impulses are transmitted from one neuron to
another, there is a Synapse.

15. POSTERIOR COLUMNS OF GRAY MATTER
 These are stimulated by sensory impulses from the periphery of the body.
 The nerve fibers of these cells contribute to the white matter of the cord.
 They transmit the sensory impulse upwards to the brain.

16. POSTERIOR COLUMNS OF GRAY MATTER
These are composed of the lower motor neurons that are stimulated by the upper
motor neurons or the connector neurons linking the anterior and posterior columns
to form reflex arcs.

17. WHITE MATTER
The white matter is arranged in 3 columns:
Anterior, Posterior and Lateral.
These tracts are formed by –
a) Sensory nerve fibers
ascending to the brain
b) Motor nerve fibers
descending from the brain
c) Fibers of the Connector
Neurons.

18. SENSORY NERVE TRACTS IN THE SPINAL CORD
 Neurons that transmit impulses towards the brain are called Sensory or Afferent
or Ascending.
 There are two main sources of sensation transmitted to the brain via spinal cord.
a) The skin – Sensory receptors or nerve endings in the skin are stimulated by
pain, heat, cold, touch and pressure.
b) The tendons, muscles and joints – Sensory receptors are specialized nerve
endings in these structures, called Proprioceptors, stimulated by stretch. Together with
impulses from eyes and ears, they are associated with the maintenance of balance and
posture, perception of body’s position in space. These nerve impulses have two
destinations:
- The impulses reach the opposite hemisphere of the cerebrum.
- The impulses reach the same hemisphere of the cerebrum.

19. SENSORY NERVE TRACTS IN THE SPINAL CORD

20. MOTOR NERVE TRACTS IN THE SPINAL CORD
Neurons that transmit nerve impulses away
from the brain are Motor or Efferent or
Descending neurons. Stimulation of the motor
neurons results in:
a) Contraction of Skeletal or
Voluntary muscle
b) Contraction of Smooth or
Involuntary muscle, cardiac muscle
and secretion by glands controlled by
autonomic nervous system

21. VOLUNTARY MUSCLE MOVEMENT
The contraction of muscles that move the
joints are under voluntary control originated in
the cerebrum.
Skeletal muscle activity is regulated by output
from the midbrain, brain stem and
cerebellum.
Efferent nerve impulses are transmitted from
the brain to other parts of the body via nerve
fibers in the spinal cord. The motor pathway
from the brain to the muscle are made of two
tract – pyramidal and extra pyramidal.

22. UPPER MOTOR NEURON
This has its cell body in the primary
motor area of the cerebrum.
The axons pass through the pons and
medulla.
These axons make up the pyramidal
tracts and decussate in the medulla
oblongata.

23. LOWER MOTOR NEURON
It has its cell body in the gray matter of spinal cord. Its axons join with the sensory
fibre and form the Mixed Spinal Nerve.
Near its termination in skeletal muscle the axon branches into many tiny fibres, each
of which is in close association with sensitive area on the muscle fibre membrane
known as Motor End Plate.
Each nerve supply every muscle.
The neuro-transmitter that transmits the nerve impulse across the synapse to
stimulate a skeletal muscle fiber is Acetylcholine.
The lower motor neuron is the final common pathway for the transmission of nerve
impulses to the skeletal muscles.

24. LOWER MOTOR NEURON

25. INVOLUNTARY MUSCLE MOVEMENT
1) Upper Motor Neuron: These have their cell
bodies in the brain at a level below the
cerebrum. They influence muscle activity that
maintains posture and balance, coordinates
skeletal muscle movements and controls
muscle tones.
1) Spinal Reflex: These consists of three
elements; a) sensory neuron
b) connector neuron
c) lower motor neuron.

26. REFLEX ARC
A reflex action is an involuntary and immediate motor response to a sensory
stimulus. Many connector and motor neurons are stimulated by afferent impulse from
a small area of skin.
For example, the pain impulses initiated by touching a hot surface with finger are
transmitted to the spinal cord by sensory fibers in mixed nerves. These stimulates
many connector and lower motor neurons resulting in contraction of skeletal muscles
causing removal of the finger.

27. REFLEX ARC

28. STRETCH REFLEX
Only two neurons are involved where the lower motor neuron is stimulated
directly by sensory neuron. No connector neuron is involved.
Example, the Knee Jerk Reflex – by tapping the tendon just below
the bent knee, the sensory nerve endings in tendon and thigh muscles are stretched.
This initiates a nerve impulse which passes into spinal chord resulting sudden
contraction of thigh muscle and the foot kicking forward. This is used as test of
integrity of reflex arc.
This reflex has a protective function which prevents excessive joint movements
resulting damage in tendons, ligaments and muscles.

29. STRETCH REFLEX

30. AUTONOMIC REFLEX
These include the pupillary light reflex when the pupil immediately constricts in
response to bright light preventing retinal damage.

31. BLOOD SUPPLY
o Anterior spinal artery - branch of the vertebral artery, supplies the anterior
2/3 of the spinal segment.
o Left and right posterior spinal arteries - The pair posterior branches of
the vertebral artery supply the posterior 1/3 of the spinal segment.
o Radiculo-medullary branches & Costo-cervical trunk - anastomose to
supply the cervical region of the spinal cord.

32. NERVE SUPPLY
There are 31 spinal nerve pairs
(mixed) that arise from the both sides
of the vertebral column:
o 8 Cervical nerves
o 12 Thoracic nerves
o 5 Lumber nerves
o 5 Sacral nerves
o 1 Coccygeal segment

33. CLINICAL SIGNIFICANCE
Spinal cord disorders or injuries may include:
o Traumatic
o Vertebral compression fractures
o Infection
o Tumors, malignancy
o Disc herniations
o Spinal stenosis, degenerative conditions.
The extent of disability depends on the level of injury and underlying degree of
severity of the corresponding clinical pathology.

34. TAKE HOME POINTS
The spinal cord is the most important structure and a vital nervous tissue link between
body and the brain.
It is covered by the three membranes of the CNS, the outer duramater, the middle
arachnoid mater and the innermost piamater.
The spinal cord extends from Foramen Magnum and terminates at first Lumber Vertebrae.
Nerves conveying impulse from the brain to the various organs and tissue descend through
the spinal cord.
The spinal cord comprises 5 segments, Cervical, Thoracic, Lumbar, Sacral and Coccygeal.
 It is made up of grey matter in the middle and white matter towards periphery.