Dermatomes, myotomes, segmental innervation of the limbs Flashcards

1
Q

what does the sclerotome form and where is it found

A

vertebrae and ribs

found ventrally

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2
Q

what does the dermatomyotome form and where is it found

A

dermis and muscle

dorsal

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3
Q

how does the DMT form

A

develop in association with a specific neural level of spinal cord
take nerve supply with them from neural tube as spinal segmental nerve

skin and muscle derived from a single dermamyotome have a common spinal nerve supply

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4
Q

spinal nerve roots

A

roots connect each spinal nerve to a segment of cord which is continuous

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5
Q

dorsal roots contain

A

afferent/ sensory nerve fibres only

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6
Q

dorsal root ganglion

A

cell bodies of the sensory neurons from the periphery

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7
Q

ventral roots contain

A

efferent/ motor and autonomic nerve fibres only

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8
Q

where does the spinal cord run through

A

vertrebral foramen which join to form the spinal canal

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9
Q

where do spinal nerves leave the spinal canal

A

intervetrebral foramina

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10
Q

where does the spinal cord start and end

A

inferior margin of medulla oblongata and ends at the conus medullaris at L2

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11
Q

where do the first pair of spinal nerves emerge

A

emerge between occipital bone and atlas (C1)

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12
Q

where do the cervical spinal nerves emerge

A

c1 - c7 exit above corresponding vertebrae

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13
Q

where does the c8 spinal nerve emerge

A

between c7 and t1

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14
Q

where do the T1-L5 spinal nerves emerge

A

below corresponding vertebrae

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15
Q

where do S1 - S4 exit

A

Via 4 pairs of sacral foramina

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16
Q

where does s5 and Co1 exit

A

sacral hiatus

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17
Q

what does the posterior/ dorsal ramus supply

A

deep muscles and skin of dorsal trunk
divides again into medial and lateral branches
supply skin of back in ‘tidy’ segmental manner
narrow strip of muscle/ skin in line with intervetrebral foramen

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18
Q

what does the anterior/ ventral ramus supply

A

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

enter the plexuses to supply the limbs

19
Q

what is the meningeal branch supply

A

re-enters spinal canal through intervetrebral foramen

supplues vetebrae, ligaments, blood vessels and meningies

20
Q

where does the brachial plexus supply

A

upper limb

21
Q

where does the lumbo-sacral plexus supply

A

lower limb

22
Q

axial line

A

junction of two dermatomes supplied from discontinuous spinal levels

they mark the centre of either the ventral or dorsal compartments of the limb

23
Q

how do the upper limbs rotate

A

lateral rotation away from the pre-axial border

24
Q

how do lower limbs rotate

A

medial rotation towards the pre-axial border

25
in the upper limb what marks the pre/post-axial border
cephalic vein | basilic vein
26
in the lower limb what marks the pre/post-axial border
long saphenous vein | short saphenous vein
27
peripheral nerve territories
these are the areas of the skin supplied by the peripheral nerves - branches of brachial plexus in upper limb - branches of lumbosacral plexus in lower limb they often overlap sections of multiple dermatomes (consistent with their spinal nerve content)
28
What is the difference between a myotome and motor unit
A myotome is a group of muscles supplied by a spinal nerve (which contains multiple motor neurons), whereas a motor unit is a single motor neuron and the skeletal muscle fibres it innervates.
29
what does the C5 myotome do
shoulder abduction and external rotation
30
C6 myotome
elbow flexion / wrist extension / supination
31
c7 myotome
elbow extension / wrist flexion / pronation
32
c8 myotome
finger flexion / finger extension
33
t1 myotome
finger abduction and adduction
34
l2 myotome
hip flexion
35
l3 myotome
knee extension
36
l4 myotome
ankle dorsiflexion
37
l5 myotome
great toe extension
38
s1 myotome
ankle plantar-flexion
39
s2 myotome
great toe flexion
40
what is hiltons law
The nerves crossing a joint supply: • The muscles acting on it • The skin over the insertion of those muscles • The joint itself
41
dermatome
A dermatome is an area of skin supplied by a single spinal nerve.
42
Why do the areas of skin that constitute the dermatomes often differ from those supplied by the peripheral nerves?
A dermatome is an area of skin supplied by a single spinal nerve. A peripheral nerve, however, often contains fibres from multiple spinal nerves. In the limbs, the spinal nerve fibres are distributed via the brachial (upper limb) and lumbosacral (lower limb) plexuses into multiple different peripheral nerves. Fibres from one spinal nerve can enter multiple different peripheral nerves, and peripheral nerves can contain fibres from multiple spinal nerves.
43
State four factors that contribute to the stability and mobility of the vertebral column
* The thickness and compressibility of the intervertebral discs * The shape and orientation of the intervertebral facet joints * The tone of the back muscles * The resistance of the ligaments of the vertebral column.