Spinal Cord And Nerves

Question 1

The Spinal Cord

Answer 1

• It is found in the spinal canal.
• It is continuous with the brain stem.
• The spinal cord is attached to the coccyx at 8
weeks in utero.
• In the newborn the spinal cord level is at L3.
• In the adult the spinal cord ends at L1-L2, but
never below L2.
• The conus medullaris ends at L2.
• The spinal cord is made up of white and gray
matter.
• The filum terminale is from L2-Coccygeal

Question 2

Spinal Cord Position

Answer 2

• In the embryo, the spinal cord extends the entire length of the vertebral column and the spinal
nerves pass through the intervertebral foramina at their levels of origin.

• The vertebral column and dura mater grow at a faster rate than the spinal cord, therefore the
caudal end of the spinal cord terminates at a
higher level as development continues.

• During the sixth month of gestation the caudal tip of the spinal cord lies at the level of S1.

• At birth, it lies at the level of L3, while in
the adults it ends at L1-L2.

• As a result of the different rates of growth,
the spinal roots run obliquely from the cord
to their corresponding vertebral level.

• The roots below the caudal end of the cord
form a bundle of nerve roots called the
cauda equina.

Question 3

Spinal Nerves, number

Answer 3

• 31 pairs:
• 8 cervical nerves (7 cervical vertebrae)
• 12 thoracic nerves
• 5 lumbar nerves
• 5 sacral nerves
• 1 coccygeal nerve (4 coccygeal vertebrae)

There are 23 intervertebral discs - 6 Cervical - 12 Thoracic - 5 Lumbar

Question 4

Spinal nerves, description

Answer 4

• Cn1 (suboccipital nerve) between skull and the atlas.
• Cn1 has no dorsal root but it has a dorsal ramus.
• Cn2-7 exit the vertebral column ABOVE their corresponding
vertebrae.
• Cn8 passes BELOW C7, between C7 and T1.
• All thoracic nerves (Tn1-12) pass BELOW their corresponding vertebral level.
• All lumbar nerves (Ln1-5) exit BELOW their corresponding level.
• All sacral nerves and coccygeal nerve exit BELOW their corresponding vertebral level.

Question 5

Coverings of the Spinal Cord

Answer 5

DURA MATER:
• Fibrous sheath
• Ends at S2 and it becomes
filamentous surrounding the filum terminale
• The epidural space is between the bone and the dura mater

ARACHNOID MATER:
• Ends at S2
• The space between the
arachnoid and pia = subarachnoid space (contains the CSF)

PIA MATER:
• Closely invests the cord
• It has lateral projections between the dorsal and ventral spinal roots = denticulate ligaments
• At the conus medullaris it continues as a thread to cover the filum terminale
• Therefore, the filum terminale is made up of pia mater from L2-S2, and of pia and dura from S2- coccyx.

Question 6

Layers of the Spinal Cord

Answer 6

1. Vertebral bodies (bone)
2. Epidural space
   • Fat
   • Vertebral venous plexus (of Batson)
   • Spinal nerves
   • Contains the CSF
3. Dura mater
4. Subdural space
5. Arachnoid mater
6. Subarachnoid space
7. Pia mater
8. Spinal cord

Question 7

Blood & Nerve Supply of the Spinal Cord

Answer 7

ARTERIAL SUPPLY:
• Anterior Spinal artery
(vertebral artery) in the anterior median sulcus
• Segmental arteries
• Two Posterior Spinal arteries (vertebral artery) lateral to the posterior medial sulcus
• Radicular arteries (intermediate neural artery)

VENOUS DRAINAGE:
• Into the intervertebral veins, and then into the segmental veins or vertebral venous plexus
• Vertebral Venous Plexus of Batson
• Found in the epidural space
• It has no valves
• Drains into the Superior Sagittal Sinus of the brain

NERVE SUPPLY:
• Meningeal branches from the spinal nerves