Spinal cord, spinal nerves and meninges Lecture

Question 1

What is the relation between the spinal cord and meninges?

Answer 1

They are part of the CNS. The spinal cord is found within the vertebral canal and is covered by 3 layers of the meninges.

Question 2

What are the meninges?

Answer 2

3 membranes, surrounding, protecting and suspending the brain and spinal nerves. Contains CSF in the subarachnoid space.

Question 3

What are the 3 layers of meninges?

Answer 3

Dura mater, arachnoidea mater, and pia mater

Question 4

What is the dura mater?

Answer 4

Thickest layer, divided into 2; the periosteal layer, and the inner meningeal layer.

Referred to as the dural sac in the vertebral canal, and is not attached to bone. Ends at the lower border of S2 and fuses with terminale. Covers root of spinal nerves into intervertebral foramina.

Question 5

What is the epidural/extradural space?

Answer 5

Found between the periosteum and the dura, extends between the foramen magnum, and the sacral hiatus. Contains internal vertebral plexus within fatty tissue.

Question 6

What is the arachnoidea mater?

Answer 6

Deep to and in contact with the dura mater. Subarachnoid space is between the arachnoidea and pia mater, and ends at the lower border of S2. Lumbar cistern is found between L1/2 and S2, and contains CSF and blood vessels.

Question 7

What is pia mater?

Answer 7

The inner most layer, a thin vascular layer closely adhered to the spinal cord, also covers the surface of spinal roots. Becomes filum terminale at the tip of the conus medullaris, and condenses to form denticulate ligaments between the roots of spinal nerves.

Question 8

What is the vertebral canal?

Answer 8

The vertebral canal is a hollow tube like structure made of all the individual vertebral foramens of the vertebrae. The spinal cord and associated vessels run through here.

Question 9

How does the spinal cord develop?

Answer 9

THe vertebral column grows faster than the spinal cord; 8wks (embryo), the spinal cord and vertebral column are equal lengths. In neonates, the spinal cord ends at L3 vertebra, and in adults, the spinal cord extends from the foramen magnum to disc between L1/L2.

Question 10

Overview of the spinal cord

Answer 10

Begins at foramen magnum, ends at L1/L2. Inferior end is conus medullaris which narrows as filum terminale

Question 11

Where is the spinal cord enlarged?

Answer 11

Cervical enlargement between C4-T1 (brachial plexus)

Lumbosacral enlargement between T11 - S1 (lumbosacral plexus)

Question 12

What are the internal features of the spinal cord? (Gray Matter)

Answer 12

Dorsal/Posterior horns - inter-neurons
Lateral horns - visceral neurons
Ventral/Anterior horns - somatic motor neurons

Central canal

Question 13

What are the internal features of the spinal cord? (White Matter)

Answer 13

Ventral/anterior columns, lateral columns and dorsal/posterior horns.

Question 14

What are the segments of the spinal cord?

Answer 14

Cervical (8)
Thoracic (12)
Lumbar (5)
Sacral (5)
Coccygeal (1)

Question 15

What are the different spinal rami?

Answer 15

Dorsal rami (mixed) carry motor fibres to back muscles, sensory fibres from back skin to vertebral joints and sympathetic neurons to blood vessels and sweat glands of the skin of the back.

Ventral rami (mixed) motor fibres to intercostal muscles, sensory fibres from thoracic skin and parietal pleura and vertebral joints, and sympathetic fibres to blood vessels and sweat glands of the skin.

Question 16

How are spinal nerves numbered?

Answer 16

In the cervical region, numbered according to the vertebrae below, and below T1, numbered according to the vertebra above.

Question 17

Order of development of spinal nerve

Answer 17

Rootlets converge → roots, then converge → spinal nerve (mixed, motor & sensory) which divide → ventral + dorsal rami (mixed, motor & sensory nerve fibres).

Question 18

What is a nerve plexus?

Answer 18

Ventral rami of spinal nerves may join with others to form nerve plexuses.

Question 19

What is a reflex?

Answer 19

Rapid, involuntary, motor response to a stimulus

Question 20

What is a reflex arc?

Answer 20

Receptor, sensory neuron, integration centre, motor neuron, and effector organ.

Question 21

What is a spinal reflex?

Answer 21

Somatic spinal reflexes provide information on the integrity of the reflex pathway and degree of excitability of the spinal cord.

Question 22

What is the cauda equina?

Answer 22

Lower spinal segments of the spinal cord lie adjacent to vertebrae above their own level.
The lower 1/3 of the v.canal contains the roots of spinal nerves or L2, and the filum terminale. The cauda equina is the roots of lower lumbar and sacral spinal nerves, within the lumbar cistern.

Question 23

What is a lumbar puncture, why and how is it performed?

Answer 23

Used to sample CSF for blood/organisms, or measure the CSF pressure, or injection of anaesthetics.

Performed between L3/L4 or L4/L5 because there is plenty of CSF in the lumbar cistern and lower risk of coming into contact with significant anatomical structures.