Lecture 9: Anatomy of Spinal Cord

Question 1

What is the Spinal Cord:

Answer 1

The spinal cord is a continuation of the brainstem and is part of the CNS.

It is situated inside the vertebral canal.

Question 2

What are the dimensions of the spinal cord?

Answer 2

It is 40–50 cm long and 1–1.5 cm in diameter.

Question 3

At what age does the spinal cord finish growing compared to the vertebral column?

Answer 3

The spinal cord stops growing at age 4, while the vertebral column finishes growing at ages 14–18.

Question 4

Where does the spinal cord terminate?

Answer 4

It ends at the L1/L2 vertebra as the conus medullaris.

Question 5

How many spinal cord segments are there and how are they distributed?

Answer 5

there are 31 segments defines by 31 pairs of nerves exiting the cord

Cervical: 8

Thoracic: 12

Lumbar: 5

Sacral: 5

Coccygeal: 1

Question 6

Through what structure do dorsal and ventral roots enter and leave the vertebral column, and how is this location determined?

Answer 6

They enter and leave through the intervertebral foramen at the vertebral segments corresponding to the spinal segment.

Question 7

What are the two enlargements of the spinal cord and their function?

Answer 7

Cervical Enlargement (C3–T1): Innervates upper limbs

Lumbosacral Enlargement (L1–S2): Innervates lower limbs

Question 8

What is the filum terminale?

Answer 8

A strand of fibrous tissue extending from the conus medullaris to 1st coccygeal vertebra (Co1), anchoring the spinal cord.

Question 9

What are the three meningeal layers covering the spinal cord?

Answer 9

1. Dura mater
2. Arachnoid mater
3. Pia mater.

Question 10

What is found between the arachnoid and pia mater?

Answer 10

The subarachnoid space filled with cerebrospinal fluid (CSF).

Question 11

What is the lumbar cistern and its clinical significance?

Answer 11

It’s the CSF-filled subarachnoid space below the conus medullaris; it’s the site for lumbar puncture.

Question 12

What anchors the spinal cord laterally to the dura?

Answer 12

Denticulate ligaments (from the pia mater).

Question 13

What surrounds the central canal of the spinal cord?

Answer 13

A single layer of ependymal cells.

Question 14

Describe the arrangement of gray and white matter in the spinal cord.

Answer 14

Gray matter: Butterfly/H-shaped, central region (contains cell bodies).

White matter: Peripheral, contains myelinated/unmyelinated fibers.

Question 15

What happens to gray matter ratio in lower spinal cord levels?

Answer 15

The gray-to-white matter ratio increases because fewer nerve fibers pass through lower levels.

Question 16

What features are seen in a transverse section of the adult spinal cord?

Answer 16

White matter at the periphery with myelinated and unmyelinated nerve fibers

Gray matter inside, containing cell bodies

A central canal filled with CSF, lined by a single layer of ependymal cells

Question 17

What are the four gray matter columns?

Answer 17

Dorsal horn: Found in at all spinal cord levels and comprised of Sensory Nuclei input

Intermediate column & Lateral horn: Comprises of Autonomic control

Ventral horn: Motor Neurons output

Question 18

What are the three columns of white matter?

Answer 18

Dorsal (posterior) column

Lateral column

Ventral (anterior) column

Question 19

What surrounds the gray matter in the spinal cord and what is its function?

Answer 19

White matter surrounds the gray matter and contains myelinated and unmyelinated nerve fibers that conduct information up (ascending) and down (descending) the spinal cord.

Question 20

What is the dorsal root composed of?

Answer 20

Axons from primary sensory neurons in the dorsal root ganglia, transmitting sensory input.

Question 21

Dorsal root ganglia receives information from:

Answer 21

skin, skeletal muscle and joints to be relayed to the spinal cord

Question 22

What is the ventral root composed of?

Answer 22

Motor and visceral efferent fibers that emerge as ventral rootlets.

Question 23

What forms the spinal nerve root?

Answer 23

The union of dorsal and ventral roots within the intervertebral foramen.

Question 24

What do the dorsal and ventral rami of spinal nerves innervate?

Answer 24

the dorsal primary nerves (ramus) – innervates the skin and muscles of the back

the ventral primary nerves (ramuss)- – innervates the ventral lateral muscles and skin of the trunk, extremities and visceral organs

Question 25

How do cervical spinal nerves exit the vertebral column?

Answer 25

C1–C7: Exit above their vertebrae C8: Exits below C7, between C7 and T1

Question 26

What is the cauda equina?

Answer 26

Bundle of lumbosacral nerve roots traveling downward before exiting the spinal cord.

Question 27

What defines a spinal segment?

Answer 27

A section of spinal cord with one pair of dorsal and ventral roots, forming a single spinal nerve.

Question 28

Why do spinal nerve roots travel longer distances in the thoracic and upper lumbar regions, and what are the lumbosacral roots called?

Answer 28

In the thoracic and upper lumbar regions, the spinal cord level is about three segments higher than the vertebral level, so root filaments must travel longer distances to reach their intervertebral foramen. The lumbosacral roots that descend in a bundle are called the cauda equina.

Question 29

What spinal structures are shown in the longitudinal section of the spinal cord

Answer 29

Conus Medullaris: The tapered end of the spinal cord (around L1–L2) Cauda Equina: Bundle of spinal nerve roots below the conus medullaris Filum Terminale: Fibrous extension from the conus to the coccyx (anchors the cord) Spinal Nerve Roots: Exit through intervertebral foramina corresponding to spinal segments Lumbar Cistern: CSF-filled subarachnoid space below the conus (site for lumbar puncture)

Question 30

LO: Describe the spinal growth and segments

Answer 30

GROWTH: The spinal cord finishes growing at the age of 4, while the vertebral column finishes growing at age 14-18. TERMINATION: The spinal cord typically ends at the level of the L1/L2 vertebra, forming the conus medullaris. SEGMENTAL SHIFT: Due to differential growth between the cord and vertebral column, spinal nerves originating from lower cord segments must travel further downward within the vertebral canal to exit at the correct intervertebral foramen, especially noticeable in the cauda equina.

Question 31

LO: Explain the layers covering the spinal cord

Answer 31

Protected by 3 meningeal layers; 1. Dura Mater (outermost): 2. Arachnoid Mater (middle layer): 3. Pia Mater (innermost layer):

Question 32

Dura Matter is

Answer 32

A tough, fibrous sheath forming the dural sac. It ends at S2, below which lies the filum terminale externum.

Question 33

Arachnoid Mater is

Answer 33

A thin, avascular membrane adhering to the inner surface of the dura. The subarachnoid space beneath it contains cerebrospinal fluid (CSF) and ends at S2.

Question 34

Pia Matter is

Answer 34

A delicate membrane directly covering the spinal cord surface. It extends as: Denticulate ligaments: Tooth-like lateral extensions anchoring the spinal cord to the dura. Filum terminale: A fibrous strand anchoring the conus medullaris to the coccyx.

Question 35

LO: Explore the internal structure of the spinal cord

Answer 35

A transverse section of the spinal cord reveals: Gray Matter (central): H-shaped or butterfly-shaped and composed of: - Dorsal horn: Sensory neurons - Ventral horn: Motor neurons - Lateral horn: (Only in T1–L2) contains autonomic neurons - Intermediate zone: Interneurons White Matter (peripheral): Contains ascending (sensory) and descending (motor) myelinated and unmyelinated axons. Divided into: - Dorsal (posterior) columns - Lateral columns - Ventral (anterior) columns - Central Canal: Runs through the center, filled with CSF, and lined by ependymal cells.

Question 36

Gray-to-White Matter Ratio:

Answer 36

More gray matter is seen in cervical and lumbar enlargements (due to limb innervation), and more white matter is found in higher spinal levels due to greater accumulation of ascending/descending fibers.

Question 37

LO: Identify the structure and function of the spinal roots

Answer 37

Dorsal (Posterior) Root: - Contains afferent (sensory) fibers. - Neurons are located in the dorsal root ganglion (DRG). - Transmits sensory information into the spinal cord Ventral (Anterior) Root: - Contains efferent (motor and autonomic) fibers. - Arises from motor neurons in the ventral and lateral horns. - Carries signals from the spinal cord to muscles and glands.

Question 38

The Conus Medullaris... a) exhibits both a cervical and lumbar enlargement b) has a modification of neural tissue extending from its termination to the coccygeal ligament c) gives origin to most of the cauda equina d) is found at its lowest extent at S2 e) is normally anaesthetised to perform a spinal tap

Answer 38

C

Question 39

A neuron with a cell body in the dorsal root ganglia could convey what type of fibers? a) motor to the deep back muscles b) motor to the pectoralis major muscle c) sensory from the skin overlying the trapezius d) sympathetic preganglionics to the suprarenal medulla e) visceral efferents to the stomach

Answer 39

C

Question 40

The denticulate ligament is... a) is a modification of a pia mater b) is found between all dorsal and ventral roots c) attaches to the dural sac continuously d) has its terminal attachment at S2 e) holds the radicular arteries in place

Answer 40

A

Question 41

A patient is suspected of having a bacterial meningitis. As part of the diagnostic procedure, a lumbar puncture is to be performed. the attending physician asks you where you should insert the spinal needle to withdraw CSF. just below the spine of the 4th lumbar vertebrae, what reference point would you use to identify the spine? a) crest of the illium b) ischial tuberosity (Too low) c) pubic symphysis (too low) d) umbilicus (too high) e) xiphoid process (too high)

Answer 41

A

Question 42

As the spinal needle in the above question is being inserted, which ligament would it pass through on its way to the subarachnoid? a) Anterior longitudinal b) Denticulate c) Ligamentum nuchae d) posterior lonitudinal e) Supraspinous

Answer 42

E

Question 43

The number of vertebrae and number of spinal cord segments are the same in each region except; a) cervical b) thoracic c) lumbar d) sacral

Answer 43

A

Question 44

if in the process of doing a lumbar puncture a spinal needle was inserted posteriorly in the midline until it had just penetrated the posterior longitudinal ligament, would the needle have entered the subarachnoid space? a) yes b) no

Answer 44

Yes

Question 45

While moving into a new apartment a student lifting a heavy box of books experiences a sharp pain in the back, radiating down the anterior thigh and medial side of his leg. after several days of misery, he finally goes for treatment and is told that he has a herniated IVD at L4 level which is compressing a spinal nerve where it exist the vertebral column. the point of compression is the; a) central canal b) foramen magnum c) hiatus of the sacral canal d) Intervertebral foramen e) vertebral foramen

Answer 45

c) hiatus of the sacral canal

Question 46

In order to expose the spinal cord fro the posterior side, it is necessary to remove the; a) laminae, pedicles and ligamentum flavum b) laminae, SP and ligamentum flavum c) Pedicles, SP and PLL d) TP, pedicles and ligamenta flavum

Answer 46

B

Question 47

inserting a spinal tap needle in the lumbar region, in the midline, you hear and feel a pop at the needle tip. what structure was perforated to cause the pop a) IVD b) ALL c) Ligamentum Flavum d) Dura mater e) Arachnoid mater

Answer 47

D

Question 48

A 45 year old man complained to his physician that the muscles of his upper limb were weak and he felt clumsy while walking. tests revealed that he had amyotrophic lateral sclerosis, (lou gehrig disease), a-disease which attacks the neurons of the voluntary motor system. where would one expect to see atrophic or degenerated nerve cell bodies. a) dorsal horn of the spinal cord b) Dorsal root ganglion c) Lateral horn of the spinal cord d) Sympathetic chain ganglia e) Ventral horn of the spinal cord

Answer 48

E