External and internal features of the spinal cord

Question 1

Where does the spinal cord begin and terminate in adults?

Answer 1

Begins at the medulla oblongata (foramen magnum) and terminates between L1 and L2 (conus medullaris).

Question 2

How does the termination differ in newborns?

Answer 2

Terminates at L3 at birth.

Question 3

Name the three meningeal layers covering the spinal cord.

Answer 3

Dura mater, arachnoid mater, pia mater.

Question 4

What is the function of the denticulate ligaments?

Answer 4

Anchor the spinal cord laterally to the dura mater.

Question 5

What structure does the pia mater form inferiorly?

Answer 5

Filum terminale.

Question 6

What is found in the epidural space?

Answer 6

Fatty tissue and venous plexus (site of epidural anesthesia).

Question 7

What does the subarachnoid space contain?

Answer 7

CSF, nerve roots, and spinal arteries (extends to S2).

Question 8

What are the two enlargements of the spinal cord, and what do they supply?

Answer 8

Cervical enlargement (C3–T2): Upper limbs.

Lumbosacral enlargement (L1–S3): Lower limbs.

Question 9

What are the three horns of the grey matter?

Answer 9

Anterior horn: Motor neurons.

Posterior horn: Sensory neurons.

Lateral horn (T1–L3): Autonomic (sympathetic) neurons.

Question 10

What is the cauda equina?

Answer 10

Bundle of lumbosacral nerve roots below the conus medullaris (resembles a horse’s tail).

Question 11

Where is Clarke’s nucleus located, and what is its function?

Answer 11

Base of posterior horn (C8–L3); relays unconscious proprioception to the cerebellum.

Question 12

Which tracts carry pain/temperature and proprioception?

Answer 12

Pain/temperature: Lateral spinothalamic tract.

Proprioception: Dorsal columns (gracilis/cuneatus) and spinocerebellar tracts.

Question 12

What is the function of the substantia gelatinosa?

Answer 12

Processes pain, temperature, and touch (forms contralateral spinothalamic tract).

Question 13

Which tract regulates extensor tone?

Answer 13

Vestibulospinal tract (uncrossed, from vestibular nuclei).

Question 13

What is the pathway of the corticospinal tract?

Answer 13

From motor cortex → decussates in medulla (90%) → lateral corticospinal tract → ventral horn.

Question 14

Name the major arteries supplying the spinal cord.

Answer 14

Anterior spinal artery, paired posterior spinal arteries, and segmental medullary arteries (e.g., artery of Adamkiewicz).

Question 14

What is Brown-Séquard syndrome?

Answer 14

Hemisection of the cord causing ipsilateral motor loss and contralateral pain/temperature loss.

Question 15

Why is lumbar puncture performed below L2?

Answer 15

To avoid damaging the spinal cord (cauda equina present below L2).

Question 16

How many pairs of spinal nerves are there, and how are they distributed?

Answer 16

31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.

Question 17

Why is there no C1 dorsal root?

Answer 17

The first cervical nerve (C1) typically lacks a dorsal root (sensory component).

Question 18

What is the role of the visceral afferent nucleus?

Answer 18

Receives sensory input from internal organs (T1–L3).

Question 19

Where is the phrenic nucleus located, and what does it innervate?

Answer 19

C3–C5; innervates the diaphragm.

Question 20

What is unique about the accessory nucleus?

Answer 20

Located in C1–C5/C6; innervates sternocleidomastoid and trapezius (via cranial nerve XI).

Question 21

What is the spino-olivary tract responsible for?

Answer 21

Relays proprioceptive info to the cerebellum via the olivary nucleus(crosses twice).

Question 22

Which tract is the upper-limb equivalent of the dorsal spinocerebellar tract?

Answer 22

Cuneocerebellar tract (from C2–T7 to accessory cuneate nucleus).

Question 23

What is the tectospinal tract’s function?

Answer 23

Coordinates head/neck reflexes in response to visual/auditory stimuli (crosses in midbrain).

Question 24

Why is the artery of Adamkiewicz clinically significant?

Answer 24

Major segmental artery (usually T8–L1); occlusion can cause anterior cord syndrome.

Question 24

What vessels contribute to the 3 longitudinal arteries of the spinal cord?

Answer 24

Vertebral, intercostal, lumbar, and lateral sacral arteries.

Question 24

When does spinal cord myelination complete?

Answer 24

By the end of the second year of life.

Question 25

What cells are found in the substantia gelatinosa?

Answer 25

Small neurons processing pain/temperature (synapse with spinothalamic tract).

Question 26

What is the nucleus proprius, and what does it receiv

Answer 26

Bulk of posterior horn cells; receives proprioception (vibration, 2-point discrimination).

Question 27

What deficits occur in central cord syndrome?

Answer 27

Bilateral loss of pain/temperature (spinothalamic decussation damage) with preserved proprioception.

Question 28

Why does LMN lesion cause flaccid paralysis?

Answer 28

Damage to alpha/gamma motor neurons in anterior horn → loss of muscle tone and reflexes.

Question 29

What is epidural block targeting?

Answer 29

Anesthesia in the epidural space (fat/venous plexus) without piercing dura.

Question 30

Which tract is uncrossed until it reaches the cerebellum?

Answer 30

Ventral spinocerebellar tract (crosses in spinal cord, recrosses in cerebellum).

Question 31

What modality does the anterior spinothalamic tract carry?

Answer 31

Light touch and pressure.

Question 32

How are sacral fibers arranged in the lateral spinothalamic tract?

Answer 32

Dorsolateral (sacral) to ventromedial (cervical) – somatotopic organization.

Question 33

Which spinal nerve lacks an intervertebral foramen for exit?

Answer 33

C1 (exits above the atlas).