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Semester 2-MSK > Session 3-Dermatomes, Myotomes And Segmental Innervation Of The Limbs > Flashcards

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

1
Q

What is each neural segment known as?

A

Neural level

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2
Q

Complete the sentence:

Neural tube contains ___________ cells of nervous system

A

Precursor

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3
Q

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

A

4th week

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4
Q

What does the sclerotome give rise to?

A

Vertebrae

Ribs

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5
Q

What does the dermatomyotome give rise to?

A

Dermis (dermatome)

Muscle (myotome)

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6
Q

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.

A

Neural level

Spinal (segmental)

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7
Q

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

A

TRUE

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8
Q

What do spinal nerve roots connect?

A

Each spinal nerve to a “segment” of cord

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9
Q

True or false: the spinal cord is discontinuous

A

FALSE - continuous

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10
Q

What do dorsal (posterior) roots contain?

A

Afferent/sensory nerve fibres only

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11
Q

What is the dorsal root ganglion?

A

Cell bodies of the sensory neurones from the periphery

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12
Q

What do ventral (anterior) roots contain?

A

Efferent/motor and autonomic nerve fibres only

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13
Q

What are spinal nerves?

A

Parallel bundles of axons encased in connective tissue

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14
Q

What are spinal nerves made up of?

A

Motor and sensory nerves

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15
Q

Complete the sentence:

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

A

Short

Intervertebral foramen

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16
Q

How many pairs of spinal nerves are there?

A

31

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17
Q

How are the pairs of spinal nerves numbered?

A

According to the level of vertebral column from which they emerge

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18
Q

Where is the endoneurium?

A

Around each axon

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19
Q

Where is the perineurium?

A

Around each fascicle

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20
Q

Where is the epineurium?

A

Around the entire nerve

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21
Q

True or false: vertebral segments differentiate from sclerotomes

A

TRUE

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22
Q

What is equal to 1 vertebra?

A

1 vertebral segment or 1 segment of sclerotome

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23
Q

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

A

Spinal/vertebral canal

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24
Q

How do spinal nerves leave the spinal canal?

A

Via intervertebral foramina

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25
Q

Where does the spinal cord start?

A

At inferior margin of medulla oblongata

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26
Q

Where does the spinal cord end?

A

As conus medullaris at L2

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27
Q

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

A

FALSE - not vertically aligned

28
Q

What do long roots from inferior segments descend in?

A

Cauda equina (to exit at their respective foramina)

29
Q

Where do the first cervical pair of spinal nerves emerge?

A

Between occipital bone and atlas (C1)

30
Q

Where do C1-C7 exit?

A

Above corresponding vertebrae

31
Q

Where does spinal nerve C8 exit?

A

Between vertebrae C7 and T1

32
Q

Where to spinal nerves T1-L5 exit?

A

Below corresponding vertebrae

33
Q

Where do S1-S4 exit?

A

Via four pairs of sacral foramina

34
Q

Where do S5 and Co1 exit?

A

Via sacral hiatus (posterior)

35
Q

What does the mixed spinal nerve divide into?

A

Rami

36
Q

Where is the posterior/dorsal ramus?

A

Deep muscles and skin of dorsal trunk

37
Q

Where is the anterior/dorsal ramus?

A

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

38
Q

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

A

Meningeal branch

39
Q

What does the meningeal branch supply?

A

Vertebrae
Ligaments
Blood vessels
Meninges

40
Q

What are the rami communicantes?

A

Contain components of autonomic nervous system (sympathetic)

41
Q

What does the dorsal/posterior rami divide into?

A

Medial and lateral branches

42
Q

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

A

1) Skin of back in ‘tidy’ segmental manner

2) Narrow strip of muscle/skin in line with intervertebral foramen

43
Q

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

A

Enter brachial plexus to supply upper limb

44
Q

Define myotome

A

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

45
Q

Define dermatome

A

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

46
Q

True or false: a myotome is a motor unit

A

FALSE - not a motor unit

47
Q

What is a motor unit?

A

Motor neuron and the skeletal muscle fibres it innervates

48
Q

Complete the sentences:

One spinal nerve contains neurons of _____ motor units. One spinal nerve supplies _____ myotome.

A

Many

One

49
Q

True or false: there is functional overlap between adjacent dermatomes

A

TRUE

50
Q

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

A

TRUE

51
Q

What is an axial line?

A

Junction of two dermatomes supplied from discontinuous spinal levels

52
Q

True or false: limbs only have an anterior axial line

A

FALSE - posterior too

53
Q

What do axial lines mark?

A

Centre of either ventral or dorsal compartments of limb

54
Q

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

A

Veins

55
Q

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

A

Cephalic

56
Q

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

A

Basilic

57
Q

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

A

Long saphenous

58
Q

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

A

Short saphenous

59
Q

True or false: peripheral nerve territories are not dermatomes

A

TRUE

60
Q

What are peripheral nerve territories?

A

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

61
Q

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

A

TRUE

62
Q

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

A

FALSE - can enter more than one peripheral nerve

63
Q

What causes shingles (herpes zoster)?

A

Reactivation of Varicella zoster virus (chickenpox)

64
Q

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

A

TRUE (almost always)

65
Q

What happens to the Varicella zoster virus after chickenpox?

A

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

66
Q

What are the symptoms of shingles? (2)

A

Erythema (superficial reddening of skin)

Vesicle formation

Semester 2-MSK (23 decks)

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