Dermatomes, Myotomes

Question 1

Define Neural Level anatomically and clinically

Answer 1

Anatomical: Each neural segment of the CNS

Clinical: Lowest caudal level of fully intact sensation and motor function

Question 2

What does the neural tube contain

Answer 2

Contains precursor cells of the nervous system

Question 3

What does a single dermatomyotome develop in association with?

How do they take their nerve supply with them from the neural tube

Answer 3

A specific neural level

A spinal nerve

Question 4

Define Dermatome

Answer 4

An area of skin supplied by a single spinal nerve

Question 5

What do you call the blood vessels in the epineurium

Answer 5

Vasa Nervorum

Question 6

What does a spinal nerve consist of?
What does it split into?

How does this branch re-enter the spinal canal and what does it supply

Answer 6

• Dorsal and Ventral nerve roots
• Dorsal and Ventral Rami, Meningeal branch re-enters through intervertebral foramen.

Supplies the vertebrae, ligaments of the spinal column as well as blood vessels and meninges

Question 7

What is each vertebra is derived from?

What does the spinal cord run through
What do the spinal nerves leave the canal through

Answer 7

Parts of 2 adjacent somites

Vertebral foramen
Intervertebral foramina

Question 8

Where does the spinal cord begin and end

Answer 8

Begins at Medulla Oblongata, ends at the Conus Medullaris

Question 9

What is the Cauda Equina, where does it originate?

Answer 9

A bundle of spinal nerve roots from the L2 through to Coccygeal nerve pairs, originating in the Conus Medullaris

Question 10

How many pairs of Cervial roots, and vertebrae are there?

What does this result in?
What is the exception

Answer 10

8 pairs of cervical nerve roots
7 pairs of cervical vertebrae

Cervical nerve roots exit above their corresponding vertebrae, except C8, which emerges between the C7 and T1 Vertebrae

Question 11

From T1 vertebra downwards, where does the nerve root exit in comparison to the vertebrae

Answer 11

Nerve roots exit below the corresponding vertebrae

Question 12

Where do the Sacral nerve roots exit from

Where do the S5 and Coccygeal nerve roots exit from

Answer 12

Sacral nerve roots- Exit through sacral foramina

Exit via the sacral hiatus

Question 13

Compare the Ventral and Dorsal Rami

1. What is supplied by each
2. Size

Answer 13

1. Ventral supplies muscles and skin of upper and lower limbs + Lateral and ventral trunk
   Dorsal supplies muscles and skin of dorsal trunk
2. Dorsal- Very small
   Ventral- Large

Question 14

What is the meninges?

Name the 3 layers in the order you cut when entering body

Answer 14

Membranous coverings of brain and spinal cord

Dura mater
Arachnoid mater
Pia mater

Question 15

The T1-L2 nerves give off a what?

What do all spinal nerves receive?

Answer 15

Give off a White Ramus Communicans

Receive a Grey Ramus Communicans

Question 16

What does the dorsal ramus divide into

What does it supply

Answer 16

Medial and lateral branches

A narrow strip of muscle and skin in line with the intervertebral Foramen

Question 17

What do the anterior rami of C5-T1 and L1-S5 supply?

Which nerve networks do they each enter

Answer 17

Muscles and skin of upper limbs- C5 to T1; Brachial plexus

Muscles and skin of lower limbs- L1 to S5; Lumbosacral plexus

Question 18

On the anterior trunk, why are C4 and T2 adjacent to each other?

Answer 18

C5-T1 enter brachial plexus to supply upper limbs, so no distribution on trunk

Question 19

What is an axial line?
Does functional overlap extend across one of these
What does it mark

Answer 19

The junction of 2 Dermatomes supplied from discontinuous spinal levels

NO

Marks the Centre of either the ventral/ dorsal compartments of the limb

Question 20

What is an Axial Border

Compare limb rotation of a fetus

Answer 20

At the Margins of the limbs, and mark the borders of the anterior and posterior compartments

Upper limbs rotate laterally by 90 degrees
Lower limbs rotate medially by 90 degrees

Question 21

How many routes can the axons from a single spinal nerve take through the brachial plexus, how many peripheral nerves can it emerge in

Answer 21

Axons from a single spinal nerve can follow multiple different routes through the plexus and emerge in several peripheral nerves

Question 22

Define Myotome

What is a motor unit

Answer 22

• The group of muscle fibres supplied by a single spinal nerve
• A single motor neuron and the skeletal muscle fibres it innervates

Question 23

What upper limb movement is caused by the C5 spinal nerve

Answer 23

Shoulder abduction and external rotation

Question 24

What 3 upper limb movements are caused by the C6 spinal nerve

Answer 24

Elbow Flexion
Wrist extension
Supination

Question 25

What 3 upper limb movements are caused by the C7 spinal nerve

Answer 25

Elbow extension
Wrist Flexion
Pronation

Question 26

What 2 upper limb movements are caused by the C8 spinal nerve

Answer 26

Finger Flexion

Finger Extension

Question 27

What upper limb movement is caused by the T1 spinal nerve

Answer 27

Finger abduction and Adduction

Question 28

What lower limb movement is caused by the L2 spinal nerve

Answer 28

Hip Flexion

Question 29

What lower limb movement is caused by the L3 spinal nerve

Answer 29

Knee extension

Question 30

What lower limb movement is caused by the L4 spinal nerve

Answer 30

Ankle dorsiflexion

Question 31

What lower limb movement is caused by the L5 spinal nerve

Answer 31

Great toe extension

Question 32

What lower limb movement is caused by the S1 spinal nerve

Answer 32

Ankle-plantar Flexion

Question 33

What lower limb movement is caused by the S2 spinal nerve

Answer 33

Great toe Flexion