Notion of A Mixed Spinal Nerve & The Brachial Plexus

Question 1

What is the neural tube?

Answer 1

The embryonic precursor of the brain and spinal cord.

Question 2

What are dermatomyotomes?

Answer 2

Embryonic precursors of the dermatomes and myotomes.

Question 3

What is a spinal segmental nerve?

Answer 3

Any of the pair of nerves that exit the spinal cord to supply the dermis and muscle of a dermatomyotome.

Question 4

Where does the spinal cord start and end?

Answer 4

• It starts where the medulla of the brain ends.

- It ends at the conus medullaris.

Question 5

What is the conus medullaris?

Answer 5

Where the membrane of the spinal cord tapers into a ligament known as the filum terminale.

Question 6

What is the name of the region of a vertebra though which the spinal cord passes?

Answer 6

The vertebral foramen.

Question 7

What is the name of the region of a vertebra though which spinal nerves leave the spinal canal?

Answer 7

The intervertebral foramen.

Question 8

In the cervical spinal cord, do spinal nerves emerge superior or inferior to the vertebral level at which they have their roots?

Answer 8

Superior.

Question 9

In the non-cervical spinal cord, do spinal nerves emerge superior or inferior to the vertebral level at which they have their roots?

Answer 9

Inferior.

Question 10

Where are the two enlargements of the spinal cord?

Answer 10

At the cervical and lumbar levels.

Question 11

What tissue exists between the vertebra and the dura mater of the spinal cord?

In which space is this tissue situated?

Answer 11

• Adipose tissue.

- In the epidural space.

Question 12

Where is cerebrospinal fluid located?

Answer 12

In the subarachnoid space (between the arachnoid mater and the pia mater).

Question 13

Describe the branching of a spinal segmental nerve.

Answer 13

• As it exits the intervertebral foramen, it branches into ventral and dorsal rami.
• The dorsal ramus divides further into medial and lateral branches.

Question 14

How do ventral rami differ in appearance from dorsal rami?

Answer 14

Ventral rami are larger than dorsal rami.

Question 15

Which of the rami participate in the formation of nerve plexuses?

Answer 15

The ventral ramus only.

Question 16

What anatomical structures travel with segmental nerves?

Answer 16

Their equivalent segmental arteries and veins.

Question 17

How do the dorsal roots of a spinal segmental nerve differ functionally from its ventral roots?

Answer 17

• The dorsal roots are afferent.

- The ventral roots are efferent.

Question 18

What is an interoceptor?

Answer 18

A sensory receptor which receives stimuli from within the body (as opposed to exteroceptors).

Question 19

What type of sign is a depressed reflex?

Answer 19

A depressed reflex is a lower motoneurone sign.

Question 20

What type of sign is an exaggerated reflex?

Answer 20

An exaggerated reflex is an upper motoneurone sign.

Question 21

How is autonomic supply of a segmental nerve tested?

Answer 21

By testing whether the area of its dermatome is able to sweat or not.

Question 22

Where does the lumbar plexus form?

Answer 22

Behind the psoas major.

Question 23

Where do nerves of the lumbar plexus emerge?

Answer 23

Either medial or lateral to the borders of the psoas major.

Question 24

List 4 nerves of the lumbar plexus that emerge lateral to psoas major.

Answer 24

1 - Femoral nerve.

2 - Iliohypogastric nerve.

3 - Ilioinguinal nerve.

4 - Lateral cutaneous nerve of the thigh.

Question 25

List 2 nerves of the lumbar plexus that emerge medial to psoas major.

Answer 25

1 - Obturator nerve.

2 - Lumbosacral trunk.

Question 26

Which nerve forms the sacral plexus?

Answer 26

The lumbosacral trunk.

Question 27

What are the spinal roots of the lumbosacral trunk?

Answer 27

Half of L4 and all of L5.

Question 28

List 4 regions supplied by the sacral plexus.

Answer 28

1 - The pelvic region.

2 - The gluteal region.

3 - The perineal region.

4 - The lower limb.

Question 29

Via which nerve does the sacral plexus supply the lower limb?

Answer 29

The sciatic nerve.