Back - Contents of Vertebral Canal (1)

Question 1

What marks the rostral end of the spinal cord?

Answer 1

The spinal cord begins as a continuation of the medulla of the brainstem. The spinal cord begins at the foramen magnum of the occipital bone.

Question 2

What marks the caudal end of the spinal cord?

Answer 2

The level of the L1 or L2 vertebra.

Question 3

Explain the “cervical enlargement” of the spinal cord.

Answer 3

The cervical enlargement is the section of spinal cord that is widest (thickest) in the upper spinal cord. It extends from C4 through to T1, and it represents the areas forming the brachial plexus.

Question 4

Explain the “lumbosacral enlargement” of the spinal cord.

Answer 4

The lumbosacral enlargement is the section of the spinal cord that is widest (thickest) in the lower spinal cord. It extends from T11 through to S1, and it represents the areas forming the lumbar plexus and the sacral plexus.

Question 5

What name is given to the sections of the spinal cord that are caudal to the lumbosacral enlargement?

Answer 5

The medullary cone. This is where the spinal cord tapers off into the cauda equina.

Question 6

What is meant by a “nucleus” within the CNS?

Answer 6

This is a collection of nerve cell bodies within the CNS.

Question 7

What is meant by a “tract” within the CNS?

Answer 7

This is a bundle of nerve fibers (axons) connecting neighbouring or distant nuclei of the CNS.

Question 8

What is meant by “white matter” within the CNS?

Answer 8

This represents the interconnecting fiber tract system.

Question 9

What is meant by “grey matter” within the CNS?

Answer 9

This represents the nerve cell bodies.

Question 10

Between which two layers is the CSF located?

Answer 10

Between the pia mater and the arachnoid mater.

Question 11

Describe the course of a spinal nerve, from the spinal cord to the rami.

Answer 11

From spinal cord:
Anterior and Posterior rootlets –> Anterior and Posterior roots –> unite into a “mixed spinal nerve” as it passes through the intervertebral foramen –> this then divides into posterior (dorsal) ramus and anterior (ventral) ramus.

Question 12

Which fibres (motor or sensory?) run in each of the following:

1) Ventral root
2) Dorsal root
3) Ventral ramus
4) Dorsal ramus

Answer 12

1) Motor (efferent)
2) Sensory (afferent)
3) Both
4) Both

Question 13

C4 spinal nerve exits superior or inferior to the C4 vertebral body?

Answer 13

Superior.

Question 14

T9 spinal nerve exits superior or inferior to the T9 vertebral body?

Answer 14

Inferior.

Question 15

How many spinal nerves are there in each section of the spinal cord?

Answer 15

Cervical: 8 pairs
Thoracic: 12 pairs
Lumbar: 5 pairs
Sacral: 5 pairs
Coccygeal: 1 pair

Question 16

What is the dural sac?

Answer 16

This is the long tubular sheath within the vertebral canal, adhering to the margin of the foramen magnum of the cranium, where it is continuous with the cranial dura mater. The spinal dural sac is anchored inferiorly to the coccyx by the terminal filum.

Question 17

As a nerve travels away from the spinal cord, where does its dura mater end?

Answer 17

The spinal nerve roots are ensheathed in dura mater. As the roots unite to form a mixed spinal nerve, this dura mater continues as a “dural root sleeve”. At this point, as the spinal nerve exits the IV foramen, the dura mater becomes continuous with the epineurium (the outer connective tissue covering the spinal nerves), and concurrently adheres to the periosteum lining the IV foramina.

Question 18

What are the denticulate ligaments made of?

Answer 18

Pia mater.

Question 19

What is the lumbar cistern?

Answer 19

This is the enlargement of the subarachnoid space, containing CSF, in the dural sac, caudal to the medullary cone. It is from the lumbar cistern that you take CSF in a lumbar puncture.

Question 20

Describe the contents of the subarachnoid space.

Answer 20

CSF, one anterior and two posterior spinal arteries, denticulate ligaments.

Question 21

Name the major arteries traveling in the subarachnoid space in the spinal cord.

Answer 21

One anterior spinal artery and two posterior spinal arteries.

Question 22

What is meant by the “spinal ganglion”? What is another name for it.

Answer 22

The spinal ganglion refers to the “dorsal root ganglion”. This is a collection of cell bodies of the dorsal (posterior) root. From spinal cord:
Posterior rootlets –> unite into posterior root –> ganglion –> union with anterior root to form Mixed Spinal Nerve