The document provides an overview of the anatomy of vertebrae and the spinal cord. It discusses: 1. The 33 vertebrae that make up the spinal column, which are divided into 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal vertebrae. 2. The general landmarks of vertebrae including the spinous process, transverse process, and vertebral body. 3. Details on the unique features of cervical, thoracic, and lumbar vertebrae. 4. That the spinal cord ends around the L1-L2 vertebrae and the cauda equina nerves extend below this point.

1. Anatomy of vertebrae and
spinal cord
Dr Harshanand Popalwar
MD DNB (PMR) MNAMS, PGDHM, MAHA
Specialist Grade Three,
Dept. of PMR, Safdarjung Hospital

2. Bones of the Spinal Column
33 bones, 24 are
flexible
A. Cervical - 7
B. Thoracic - 12
C. Lumbar - 5
D. Sacrum - 5 (false
vertebrae - fused
together)
E. Coccyx - 4 (false
vertebrae - fused
together)
Click on
picture

3. General Landmarks
1. Spinous
process
2. Lamina
3. Transverse
process –
4. Vertebral
notch
5. Body
6. Vertebral
foramen

4. General Landmarks
 Vertebral notch
◦ Superior
◦ Inferior

5. General Landmarks
 Intervertebral foramen

6. Cervical Vertebrae

7. Cervical Vertebrae
 First 7 vertebrae
 Identified as C1 – C7
 C1 = Atlas
 C2 = Axis

8. Atlas (C1)
• Large vertebral
foramen
• Transverse
ligament
Anterior
Posterior

9. Axial (C2)
 Odontoid process
or Dens

10. Thoracic (T1-T12)

11. Thoracic (T1-T12)

12. Lumbar (L1-L5)

13. Lumbar (L1-L5)

14. Note the differences:
1. Transverse process
2. Spinous process
3. Body

15. Sacrum

16. Intervertebral Disks

17. Intervertebral Disks

18. Principal Parts
1. 42-45 cm in length; 2.5
cm wide
2. cervical enlargement -
C4:T1 supply upper limbs
3. lumbar enlargement -
T9:T12 supply lower limbs
4. conus medullaris - tapers
off to end at L1-L2
5. filum terminale - pia
mater anchors cord to
coccyx
6. cauda equina - (horse
tail) nerves below L2

19. Things to NOTE about the Spinal
Cord
1. Cord itself ends at L1-L2 vertebrae
2. Lower nerves dangle down in the cauda
equina
3. There are 31 pairs of spinal nerves
4. spinal segment - gives rise to one spinal nerve
5. C1-C7 spinal nerves project ABOVE C1-C7
vertebrae
6. C8 spinal nerve projects below C7 vertebra
7. T1-S5 spinal nerves project BELOW T1-S5
vertebrae

20. Cross-Sectional Anatomy of the Spinal
Cord

21. Grey Matter areas vs. White
Matter areas
1. grey matter - nerve cell bodies motor & interneurons
2. white matter - myelinated axons of motor & sensory

22. Gray Matter and Spinal Roots

23. Gray Matter: Organization
 Dorsal half – sensory roots and ganglia
 Ventral half – motor roots
 Dorsal and ventral roots fuse laterally to form
spinal nerves
 Four zones are evident within the gray matter –
somatic sensory (SS), visceral sensory (VS),
visceral motor (VM), and somatic motor (SM)

24. Gray Matter: Organization

25. Spinal Nerves

26. Spinal Nerves
 Thirty-one pairs of mixed nerves arise from the spinal
cord and supply all parts of the body except the head
 They are named according to their point of issue
◦ 8 cervical (C1-C8)
◦ 12 thoracic (T1-T12)
◦ 5 lumbar (L1-L5)
◦ 5 sacral (S1-S5)
◦ 1 coccygeal (C0)

27. Spinal Nerves
Figure 13.6

28. Spinal Nerves: Roots
 Each spinal nerve connects to the spinal cord via
two medial roots
 Each root forms a series of rootlets that attach to
the spinal cord
 Ventral roots arise from the anterior horn and
contain motor (efferent) fibers
 Dorsal roots arise from sensory neurons in the
dorsal root ganglion and contain sensory
(afferent) fibers

29. Spinal Nerves: Roots

30. Nerve Plexuses
 All ventral rami except T2-T12 form interlacing
nerve networks called plexuses
 Plexuses are found in the cervical, brachial,
lumbar, and sacral regions
 Each resulting branch of a plexus contains fibers
from several spinal nerves

31. Nerve Plexuses
 Fibers travel to the periphery via several different
routes
 Each muscle receives a nerve supply from more
than one spinal nerve
 Damage to one spinal segment cannot completely
paralyze a muscle

32. Spinal Nerve Innervation: Back,
Anterolateral Thorax, and Abdominal
Wall
 The back is innervated by dorsal rami via several
branches
 The thorax is innervated by ventral rami T1-T12 as
intercostal nerves
 Intercostal nerves supply muscles of the ribs,
anterolateral thorax, and abdominal wall

33. Spinal Nerve Innervation: Back, Anterolateral
Thorax, and Abdominal Wall

35. Cervical Plexus
 The cervical plexus is formed by ventral rami of
C1-C4
 Most branches are cutaneous nerves of the neck,
ear, back of head, and shoulders
 The most important nerve of this plexus is the
phrenic nerve - the major motor and sensory
nerve of the diaphragm

36. Cervical Plexus

37. Brachial Plexus
 Formed by C5-C8 and T1 (C4 and T2 may also
contribute to this plexus in some people)
 It gives rise to the nerves that innervate the upper
limb

38. Brachial Plexus
There are four major branches of this plexus
◦ Roots – five ventral rami (C5-T1)
◦ Trunks – upper, middle, and lower, which form
divisions
◦ Divisions – anterior and posterior serve the
front and back of the limb
◦ Cords – lateral, medial, and posterior fiber
bundles

39. Brachial Plexus

40. Brachial Plexus: Nerves
 Axillary – innervates the deltoid and teres minor
 Musculocutaneous – sends fibers to the biceps
brachii and brachialis
 Median – branches to most of the flexor
muscles of arm
 Ulnar – supplies the flexor carpi ulnaris and part
of the flexor digitorum profundus
 Radial – innervates essentially all extensor
muscles

41. Brachial Plexus: Distribution of
Nerves

42. Brachial Plexus: Nerves

43. Lumbar Plexus
 Arises from L1-L4 and innervates the thigh,
abdominal wall, and related muscles
 The major nerves are the femoral and the
obturator

44. Lumbar Plexus

45. Sacral Plexus
 Arises from L4-S4 and serves the buttock, lower
limb, pelvic structures, and the related sacral
areas
 The major nerve is the sciatic, the longest and
thickest nerve of the body
 The sciatic is actually composed of two nerves:
the tibial and the common fibular nerves

46. Sacral Plexus

47. Dermatomes
 A dermatome is the area of skin innervated by the
cutaneous branches of a single spinal nerve
 All spinal nerves except C1 participate in
dermatomes

48. Dermatomes

49. White Matter in the Spinal Cord
 Fibers run in three directions – ascending,
descending, and transversely
 Divided into three funiculi (columns) – posterior,
lateral, and anterior
 Each funiculus contains several fiber tracks
◦ Fiber tract names reveal their origin and
destination
◦ Fiber tracts are composed of axons with similar
functions

50. White Matter: Pathway
Generalizations
 Pathways decussate (cross to contra lateral side
of body)
 Most consist of two or three neurons in the
pathway
 Most exhibit somatotopy (precise spatial
relationships)
 Pathways are paired (one on each side of the
spinal cord or brain)

51. Ascending (Sensory) Tracts

52. Ascending Tracts
TRACT FUNCTION
1. anterior (ventral) spinothalamic - touch and pressure to thalamus
2. lateral spinothalamic tract - pain & temperature to thalamus
3. fasciculus gracilis & cuneatus - touch, 2-pt. discrimination
conscious proprioception,
stereognosis, weight
discrimination, vibration
4. posterior spinocerebellar - subconscious proprioception
5. anterior spinocerebellar - subconscious proprioception

53. Nonspecific Ascending Pathway
 Nonspecific
pathway for pain,
temperature, and
crude touch
within the lateral
spinothalamic
tract

55. Descending (Motor) Pathways
 Motor pathways involve two neurons (upper
motor neuron and lower motor neuron)

56. Descending (Motor) Tracts

57. Descending (Motor) Pathways
TRACTS FUNCTIONS
1. Lateral & anterior corticospinal motor output from cortex motor
to cells of ant. Horn
2. rubrospinal motor from midbrain to anterior
horn for precise movement
3. tectospinal motor from midbrain to anterior
horn; movements in response to
audiovisual/cutaneous stimuli
4. vestibulospinal motor from medulla to anterior
horn; coordination/balance
5. lateral reticulospinal motor from medulla to anterior
horn; inhibit extensor reflexes
6. medial reticulospinal motor from pons to anterior horn;
facilitate extensor reflexes

58. The Direct (Pyramidal) Motor
System
 Direct pathways originate with the pyramidal
neurons in the precentral gyri
 Impulses are sent through the corticospinal tracts
and synapse in the anterior horn
 Stimulation of anterior horn neurons activates
skeletal muscles
 Parts of the direct pathway, called corticobulbar
tracts, innervate cranial nerve nuclei
 The direct pathway regulates fast and fine (skilled)
movements

59. The Direct (Pyramidal) System

61. Indirect (Extrapyramidal) Motor
System
 Includes the brain stem, motor nuclei, and all
motor pathways not part of the pyramidal
system
 This system includes the rubrospinal,
vestibulospinal, reticulospinal, and
tectospinal tracts
 These motor pathways are complex and
multisynaptic, and regulate:
◦ Axial muscles that maintain balance and
posture
◦ Muscles controlling coarse movements of the
proximal portions of limbs
◦ Head, neck, and eye movement

62. Indirect (Extrapyramidal) System

63. White Matter: Pathway Generalizations

64. Blood supply of spinal cord

67.  Thanks