Part 2 - Dermatomes And Myotomes

Question 1

What is a Dermatome?

Answer 1

Area of skin supplied by a single spinal nerve

Question 2

What is a Myotome?

Answer 2

A group of muscles supplied by a single spinal nerve

Question 3

What is an axial line?

Answer 3

The junction of two Dermatomes supplied from discontinuous spinal levels (the dermatomes may be adjacent but their spinal nerves are not)

Question 4

What do axial lines mark the centre of in limbs?

Answer 4

Ventral or dorsal compartments of the limb

Question 5

What is meant by their is functional overlap between adjacent dermatomes?

Answer 5

If the C5 spinal nerve is damaged, C6 will also supply part of C5 Dermatome and C4 will supply some of the C4 Dermatome

Really only the centre of the C5 dermatome will be affected

Question 6

Will there be any functional overlap between Dermatome that are adjacent but are separated by an axial line?

Answer 6

NO

Question 7

What is the pre-axial border of the limb buds of the embryo?

Answer 7

The border of the limb nearest to the head

Question 8

What is the post-axial border of the limb bud of the embryo?

Answer 8

The border of the limb bud closer to the tail end of the embryo

Question 9

How are the upper and lower limbs of the embryo initially orientated?

Answer 9

Begin pointing anteriorly with the thumb and great toe pointing UP

Question 10

How do the upper limbs rotate in the embryo?

Answer 10

They rotate externally so the thumbs point laterally

Question 11

How do the lower limbs rotate in the embryo?

Answer 11

Rotated medially so the great toes are on the medial aspect of the feet

Question 12

What do the pre and post axial borders of the limb mark?

Answer 12

The boundaries of the posterior and anterior compartments

Question 13

What superficial veins mark the pre axial border of the upper limb?

Answer 13

Cephalic vein

Question 14

What superficial vein marks the post axial border of the upper limb?

Answer 14

Basilic vein

Question 15

What superficial vein marks the pre axial border of the lower limb? (Approximately)

Answer 15

Great/long saphenous vein

Question 16

What superficial vein marks the post axial border of the lower limb? (Approximately)

Answer 16

Small/short saphenous vein

Question 17

What are peripheral nerves usually made up of?

Answer 17

Normally a combination of several spinal nerves

Question 18

What are some examples of peripheral nerves?

Answer 18

Femoral nerve
Obturator nerve

Question 19

Can one spinal nerve enter/contribute to multiple peripheral nerves?

Answer 19

Yes
Fibres from one spinal nerve can enter multiple peripheral nerves

Question 20

What makes up a spina nerve and where does it emerge?

Answer 20

Dorsal spinal root + Ventral spinal root

Intervertebral Foramen

Question 21

How does a spinal nerve divide/branch once it leaves the intervertebral Foramen?

Answer 21

Anterior (ventral) rami
Posterior (dorsal) rami

Question 22

For limbs, is it the dorsal (Posterior) or ventral (Anterior) rami which contribute to the plexuses to form the peripheral nerves?

Answer 22

Anterior/ventral rami

Question 23

What is the region called where all the anterior rami form their branches contributing to the formation of the peripheral nerves?

Answer 23

Plexus

Question 24

What peripheral nerves do the fibres of the anterior ramus of L2 contribute to?

Answer 24

Genitofemoral nerve
Lateral femoral cutaneous nerve
Obturator nerve
Femoral nerve

Question 25

What spinal nerve anterior rami are part of the lumbar plexus?

Answer 25

T12
L1-L5

Question 26

Where does the Obturator nerve supply?

Answer 26

Medial thigh (Upper)

Question 27

If the upper medial thigh is stimulated, how does the body detect this?

Answer 27

Sensory axons run via Obturator, through the lumbar plexus to the L2 spinal nerve, L2 dorsal root then to the L2 segment of the spinal cord

Question 28

Where does the femoral nerve supply?

Answer 28

Anterior thigh
Medial leg

Question 29

If the anterior thigh is stimulated, how does the body detect this?

Answer 29

Sensory axon runs through femoral nerve to lumbar plexus, to the L2 spinal nerve, to L2 dorsal root to the L2 segment of the spinal cord

Question 30

Where is the L2 Dermatome?

Answer 30

Proximal part of thigh and lateral part of thigh
(Above the knee)

Question 31

What spinal nerves contribute to the femoral nerve?

Answer 31

L2, L3 and L4

Question 32

What is a peripheral nerve territory?

Answer 32

Area of skin supplied by the peripheral nerves (different to Dermatome)

Question 33

Within each peripheral nerve there may be axons from ______ spinal nerves

Answer 33

MULTIPLE

Question 34

A single spinal nerve _____ contribute to formation of more than one peripheral nerve

Answer 34

CAN

Question 35

What virus causes chicken pox?

Answer 35

Varicella zoster virus

Question 36

What is the name of the disease/illness that is caused by the reactivation of the dormant chicken pox causing (Varicella Zoster virus) virus?

Answer 36

Shingles

Question 37

Why does shingles only typically affect the skin of a single Dermatome?

Answer 37

Virus remains dormant in a dorsal root ganglion after chicken pox
When reactivated travels down/through a peripheral nerve that the dorsal root ganglions spinal nerve contributes to to the skin