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MSK > 3 Dermatomes, Myotomes And Segmental Innervation Of The Limbs > Flashcards

3 Dermatomes, Myotomes And Segmental Innervation Of The Limbs Flashcards

1
Q

What are the two parts of a somite?

A

Sclerotome

Dermatomyotome

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2
Q

What does the sclerotome become?

A

Vertebrae and ribs

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3
Q

What does the dermatomyotome become?

A

Dermis (dermatome) and muscle (myotome)

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4
Q

What are dermatomyotomes?

A

Develop in association with a specific neural level of spinal cord
Take nerve supply with them from neural tube as spinal nerve
Skin and muscle derived from a single dermatomyotome have a common spinal nerve supply

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5
Q

What are spinal nerve roots?

A

Roots connect each spinal nerve to a segment of cord
Dorsal roots contain afferent/sensory nerve fibres only
Ventral roots contain efferent/motor and autonomic nerve fibres only

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6
Q

What are spinal nerves?

A

Parallel bundles of axons encased in connective tissue
Mixed (sensory and motor)
Exist briefly as they pass through the intervertebral foramen - marks division between CNS and PNS

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7
Q

How many spinal nerves are there?

A

31 pairs

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8
Q

What are the derivatives of vertebral segments?

A

Each vertebra is derived from parts of two adjacent somites

Differentiate from sclerotomes

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9
Q

Where does the spinal cord run?

A

Through vertebral foramen

Stops at L2 level

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10
Q

What is the spinal canal formed from?

A

Multiple vertebral foramina

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11
Q

How do spinal nerves leave the spinal canal?

A

Leave via intervertebral foramina

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12
Q

Where does the spin cord start and end?

A

Starts at inferior margin of medulla oblongata

Ends as conus medullaris at L2

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13
Q

What occurs to the spinal cord after L2?

A

Long roots form inferior segments descend in casual equine and exit at their respective foramina

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14
Q

Where do the spinal nerves emerge?

A

First cervical pair between occipital bone and C1
C1-C7 exit above corresponding vertebrae
Spinal nerve C8 exits between vertebrae C7 and T1
T1-L5 exit below corresponding vertebrae
S1-S4 exit via 4 pairs of sacral foramina
S5 and Co1 exit via sacral hiatus

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15
Q

What does mixed spinal nerve divide into?

A

Rami

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16
Q

What does the dorsal/posterior ramus supply?

A

Deep muscles and skin of dorsal trunk

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17
Q

What does the ventral/anterior ramus supply?

A

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

18
Q

What is the meningeal branch?

A

Comes off the spinal nerve
Re-enters spinal canal through intervertebral foramen
Supplies vertebrae, ligaments, blood vessels and meninges

19
Q

What does the dorsal/posterior rami divide into further?

A

Medial and lateral branches
Supply skin of back in tidy segmental manner
Narrow structure of muscle/skin in line with intervertebral foramen

20
Q

Where does the ventral/anterior rami go through and to?

A

Enters the plexuses to supply the limbs - brachial plexus and lumbo-sacral plexus
Segmental for the trunk
Complicated for the limbs

21
Q

What is a myotome?

A

A group f muscles supplied by a single spinal nerve or spinal nerve root

22
Q

What is a dermatome?

A

Area of skin supplied by a single spinal nerve or spinal nerve root

23
Q

What are axial lines?

A

Junction of two dermatome supplied from discontinuous spinal levels
There is functional overlap between adjacent dermatomes but not across axial lines
Axial lines mark the centre of either the ventral or dorsal compartments of the limb

24
Q

What are pre-axial and post-axial borders?

A

Boundaries of dorsal and ventral compartments
Marked by superficial veins
Upper limb: cephalon vein (pre-axial), basilic vein (post-axial)
Lower limb: long saphenous vein (pre-axial), short saphenous vein (post-axial)

25
Q

Fibres from one spinal nerve…

A

Can enter multiple peripheral nerves

26
Q

Where does the rearrangement of nerves occur?

A

Plexuses

27
Q

What are peripheral nerve territories?

A

Areas of skin supplied by the peripheral nerves
Branches of brachial plexus in upper limb
Branches of lumbosacral plexus in lower limb
Often overlap sections of multiple dermatomes

28
Q

Within each peripheral nerve there may be…

A

Fibres from more than one spinal nerve

29
Q

Fibres from one spinal nerve may enter…

A

More than one peripheral nerve

30
Q

What is a motor unit?

A

A motor neuron and the skeletal muscle fibres it innervates

1 spinal nerve supplies one myotome

31
Q

Action for C5

A

Shoulder abduction and external rotation

32
Q

Action for C6

A

Elbow flexion/wrist extension/supination

33
Q

Action for C7

A

Elbow extension/wrist flexion/pronation

34
Q

Action for C8

A

Finger flexion/finger extension

35
Q

Action for T1

A

Finger abduction and adduction

36
Q

Action for L2

A

Hip flexion

37
Q

Action for L3

A

Knee extension

38
Q

Action for L4

A

Ankle dorsiflexion

39
Q

Action for L5

A

Great toe extension

40
Q

Action for S1

A

Ankle plantar-flexion

41
Q

Action for S2

A

Great toe flexion

MSK (4 decks)

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