Session 3-Dermatomes, Myotomes And Segmental Innervation Of The Limbs

Question 1

What is each neural segment known as?

Answer 1

Neural level

Question 2

Complete the sentence:

Neural tube contains ___________ cells of nervous system

Answer 2

Precursor

Question 3

In which stage of gestation do paired somites appear in the neural tube?

Answer 3

4th week

Question 4

What does the sclerotome give rise to?

Answer 4

Vertebrae

Ribs

Question 5

What does the dermatomyotome give rise to?

Answer 5

Dermis (dermatome)

Muscle (myotome)

Question 6

Complete the sentences:

Dermatomyotomes (DMT) develop in association with a specific ______ ________ of spinal cord. They take a nerve supply with them from neural tube as _______ (_________) nerve.

Answer 6

Neural level

Spinal (segmental)

Question 7

True or false: skin and muscle derived from a single dermatomyotome have a common spinal nerve supply

Answer 7

TRUE

Question 8

What do spinal nerve roots connect?

Answer 8

Each spinal nerve to a “segment” of cord

Question 9

True or false: the spinal cord is discontinuous

Answer 9

FALSE - continuous

Question 10

What do dorsal (posterior) roots contain?

Answer 10

Afferent/sensory nerve fibres only

Question 11

What is the dorsal root ganglion?

Answer 11

Cell bodies of the sensory neurones from the periphery

Question 12

What do ventral (anterior) roots contain?

Answer 12

Efferent/motor and autonomic nerve fibres only

Question 13

What are spinal nerves?

Answer 13

Parallel bundles of axons encased in connective tissue

Question 14

What are spinal nerves made up of?

Answer 14

Motor and sensory nerves

Question 15

Complete the sentence:

The spinal nerves are very _____ and exist briefly as they pass through the ______________ _________, which marks the division between CNS and PNS

Answer 15

Short

Intervertebral foramen

Question 16

How many pairs of spinal nerves are there?

Answer 16

31

Question 17

How are the pairs of spinal nerves numbered?

Answer 17

According to the level of vertebral column from which they emerge

Question 18

Where is the endoneurium?

Answer 18

Around each axon

Question 19

Where is the perineurium?

Answer 19

Around each fascicle

Question 20

Where is the epineurium?

Answer 20

Around the entire nerve

Question 21

True or false: vertebral segments differentiate from sclerotomes

Answer 21

TRUE

Question 22

What is equal to 1 vertebra?

Answer 22

1 vertebral segment or 1 segment of sclerotome

Question 23

What is formed when multiple vertebral foramina are stacked on top of each other?

Answer 23

Spinal/vertebral canal

Question 24

How do spinal nerves leave the spinal canal?

Answer 24

Via intervertebral foramina

Question 25

Where does the spinal cord start?

Answer 25

At inferior margin of medulla oblongata

Question 26

Where does the spinal cord end?

Answer 26

As conus medullaris at L2

Question 27

True or false: most spinal cord segments are vertically aligned with the corresponding vertebrae

Answer 27

FALSE - not vertically aligned

Question 28

What do long roots from inferior segments descend in?

Answer 28

Cauda equina (to exit at their respective foramina)

Question 29

Where do the first cervical pair of spinal nerves emerge?

Answer 29

Between occipital bone and atlas (C1)

Question 30

Where do C1-C7 exit?

Answer 30

Above corresponding vertebrae

Question 31

Where does spinal nerve C8 exit?

Answer 31

Between vertebrae C7 and T1

Question 32

Where to spinal nerves T1-L5 exit?

Answer 32

Below corresponding vertebrae

Question 33

Where do S1-S4 exit?

Answer 33

Via four pairs of sacral foramina

Question 34

Where do S5 and Co1 exit?

Answer 34

Via sacral hiatus (posterior)

Question 35

What does the mixed spinal nerve divide into?

Answer 35

Rami

Question 36

Where is the posterior/dorsal ramus?

Answer 36

Deep muscles and skin of dorsal trunk

Question 37

Where is the anterior/dorsal ramus?

Answer 37

Muscles and skin of upper and lower limbs and lateral and ventral trunk

Question 38

Which other branch do spinal nerves give off that re-enters the spinal canal through the intervertebral foramen?

Answer 38

Meningeal branch

Question 39

What does the meningeal branch supply?

Answer 39

Vertebrae Ligaments Blood vessels Meninges

Question 40

What are the rami communicantes?

Answer 40

Contain components of autonomic nervous system (sympathetic)

Question 41

What does the dorsal/posterior rami divide into?

Answer 41

Medial and lateral branches

Question 42

What do the branches of the dorsal/posterior rami supply? (2)

Answer 42

1) Skin of back in 'tidy' segmental manner | 2) Narrow strip of muscle/skin in line with intervertebral foramen

Question 43

Where do the missing nerve roots in the ventral/anterior rami go?

Answer 43

Enter brachial plexus to supply upper limb

Question 44

Define myotome

Answer 44

Group of muscles supplied by single spinal nerve (or spinal nerve root)

Question 45

Define dermatome

Answer 45

Area of skin supplied by single spinal nerve (or spinal nerve root)

Question 46

True or false: a myotome is a motor unit

Answer 46

FALSE - not a motor unit

Question 47

What is a motor unit?

Answer 47

Motor neuron and the skeletal muscle fibres it innervates

Question 48

Complete the sentences: One spinal nerve contains neurons of _____ motor units. One spinal nerve supplies _____ myotome.

Answer 48

Many | One

Question 49

True or false: there is functional overlap between adjacent dermatomes

Answer 49

TRUE

Question 50

True or false: there is no functional overlap between adjacent dermatomes across an axial line

Answer 50

TRUE

Question 51

What is an axial line?

Answer 51

Junction of two dermatomes supplied from discontinuous spinal levels

Question 52

True or false: limbs only have an anterior axial line

Answer 52

FALSE - posterior too

Question 53

What do axial lines mark?

Answer 53

Centre of either ventral or dorsal compartments of limb

Question 54

What marks the pre-axial and post-axial boundaries of the ventral and dorsal compartments?

Answer 54

Veins

Question 55

Which vein in the upper limb marks the pre-axial compartment?

Answer 55

Cephalic

Question 56

Which vein in the upper limb marks the post-axial compartment?

Answer 56

Basilic

Question 57

Which vein in the lower limb marks the pre-axial compartment?

Answer 57

Long saphenous

Question 58

Which vein in the lower limb marks the post-axial compartment?

Answer 58

Short saphenous

Question 59

True or false: peripheral nerve territories are not dermatomes

Answer 59

TRUE

Question 60

What are peripheral nerve territories?

Answer 60

Areas of skin supplied by peripheral nerves eg branches of lumbar plexus

Question 61

True or false: within each peripheral nerve, there may be fibres from more than one spinal nerve

Answer 61

TRUE

Question 62

True or false: fibres from one spinal nerve enter only one peripheral nerve

Answer 62

FALSE - can enter more than one peripheral nerve

Question 63

What causes shingles (herpes zoster)?

Answer 63

Reactivation of Varicella zoster virus (chickenpox)

Question 64

True or false: shingles affects the skin of a single dermatome

Answer 64

TRUE (almost always)

Question 65

What happens to the Varicella zoster virus after chickenpox?

Answer 65

Travels through a cutaneous nerve and remains dormant in a dorsal root ganglion. When host is immunosuppressed (eg old age), virus reactivates and travels through peripheral nerve to skin of single dermatome

Question 66

What are the symptoms of shingles? (2)

Answer 66

Erythema (superficial reddening of skin) | Vesicle formation