MSK Session 4- Dermatomes, Myotomes And Segmental Innervation Flashcards

1
Q

What does the dorsal half of the degenerated somite become?

A

The dermamyotome

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2
Q

Define dermatome.

A

An area of skin supplied by a single spinal nerve.

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3
Q

Define myotome.

A

A muscle/group of muscles supplied by a single spinal nerve.

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4
Q

Define motor unit.

A

Muscle fibres innervated by a single motor nerve fibre.

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5
Q

What is the advantage of functional overlap between dermatomes? (2)

A
  • damage to a single spinal nerve is unlikely to cause anaesthesia.
  • reduced probability its of having a skin patch that has no natural sensory nerve supply.
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6
Q

Where does the spinal cord run?

A

Through the vertebral foreamen of each vertebra.

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7
Q

Where does the spinal cord start and end?

A

Start-medulla

End-L2/L3

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8
Q

Where do the spinal nerves from the spinal cord emerge?

A

Through intervertebral foramina.

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9
Q

Where in relation to the vertebra do cervical spinal nerves emerge?

A

Superior to the vertebrae.

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10
Q

Where in relation to the vertebra do non-cervical spinal nerves emerge?

A

Inferior.

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11
Q

What is a mixed segmental/spinal nerve?

A

The coming together of the dorsal and ventral roots of the spinal nerve.

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12
Q

What is the role of the dorsal roots of a spinal nerve?

A

Afferent

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13
Q

What is the role of the ventral roots of the spinal nerve?

A

Efferent

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14
Q

What is the axial line? (2)

A

The junction between dermatomes with discontinuous spinal nerves. It is also the junction between the flexor and extensor compartment.

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15
Q

Which nerve roots cause flexion at the elbow? (2)

A

C5+6

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16
Q

Which nerve roots cause extension at the elbow? (2)

A

C7+8

17
Q

Which nerve roots cause wrist flexion and extension? (2)

A

C6+7

18
Q

What is a sensory nerve territory?

A

Not a dermatome. It is an area of skin that is supplied by a peripheral nerve of the spinal root.

19
Q

Give an example of a sensory nerve territory.

A

The regimental badge area.

20
Q

What is the result of a spinal nerve lesion close to the spinal cord?

A

Loss of sensation in the dermatomes and loss of function of the myotomes.

21
Q

What is the result of a spinal nerve lesion that is more distal?

A

Loss of sensation in the peripheral nerve field.

22
Q

What does the ventral half of the degenerated somite become?

A

The sclerotome