Lecture 2: The Spinal Cord

Question 1

Explain why a lumbar puncture is carried out at the level of the second lumbar vertebrae (L2)

Answer 1

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Question 2

STUDY THE ANATOMY OF THE VERTEBRAE AND SPINAL CORD

Answer 2

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Question 3

INTERVERTEBRAL FORAMEN

Answer 3

Site where nerves going out to muscles or carrying sensory information into the spinal cord emerge.

JOINT BETWEEN 2 VERTEBRAE

Question 4

CONUS MEDULLARIS

Answer 4

The spinal cord occupies the vertebral canal extending from the brainstem at the base of the skull to the level of the second lumbar vertebrae where it tapers to form the CONUS MEDULLARIS

Question 5

MENINGES

Answer 5

Greek for membrane: Series of 3 membranes that surround the brain and spinal cord.

3 Layers of Meninges Surround the Brain and Spinal Cord in a Continuous Sheath

Dura Mater
Arachnoid
Pia Mater

Question 6

Subarachnoid

Answer 6

The space between the arachnoid and pia mater. Contains cerebral spinal fluid (CSF)

Question 7

Arachnoid

Answer 7

Smooth Outer Surface
Attaches To Dura
Meshwork That Extends To Pia

Question 8

SPECIALIZATIONS OF PIA MATER:

DENTICULATE LIGAMENT

Answer 8

Found at all levels of the spinal cord.

Projections of pia mater extending from spinal cord to inner surface of the dura mater.

Question 9

SPECIALIZATIONS OF PIA MATER:

Answer 9

DENTICULATE LIGAMENT FILUM TERMINALE

Question 10

SPECIALIZATIONS OF PIA MATER:

FILUM TERMINALE

Answer 10

Extension of pia mater that extends beyond the distal end of the spinal cord (the conus medullaris).

Conus Medullaris is at level of L2-L3. However, rootlets continue to emerge and descend to exit vertebral canal at appropriate level. Therefore, CSF must still be present below the end of the spinal cord.

Although the spinal cord ends at L2-L3, the meninges continue inferiorly to end by attaching to the coccyx. The dura and arachnoid remain as a visible dense sheath. The pia continues beyond the end of the cord as the Filum Terminale.

All 3 layers of the meninges fuse in the sacral area (S2) to form the coccygeal ligament that anchors the cord to the coccys.

Question 11

CAUDA EQUINA

Answer 11

Nerve Roots that emerge at levels below L2 extend beyond the conus medullaris to reach their exit. This forms fine filaments distal to end of the spinal cord that is called the CAUDA EQUINA.

Question 12

DORSAL AND VENTRAL ROOTS

Answer 12

At all levels of the spinal cord, nerves emerge from the dorsal lateral and ventral lateral aspect.

These are dorsal and ventral roots, respectively. These roots allow information from the periphery to enter the spinal cord (sensory input – dorsal root) and for motor commands to muscles to leave the spinal cord (motor output – ventral root).

Question 13

SPINAL CORD EXTENT

Answer 13

BASE OF SKULL - Continuous With The Medulla Of The Brain

to the

2nd – 3rd Lumbar Vertebrae

In adults, spinal cord does not extend down the entire length of the vertebral column. Instead it ends ~ L1-L2.

Therefore it is possible to withdraw CSF via a lumbar puncture (“spinal tap”) by inserting the needle below the end of the cord.

Question 14

Cervical

Answer 14

(8 segments, 7 vertebrae)

- contains cervical enlargement

Question 15

Thoracic

Answer 15

(12 segments, 12 vertebrae)

Question 16

Lumbar

Answer 16

(5 segments, 5 vertebrae)

- contains lumbar enlargement

Question 17

Sacral

Answer 17

(5 segments, 5 vertebrae)

- ends in conus medullaris