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MSK > Lecture 3 - Dermatomes and myotomes > Flashcards

Lecture 3 - Dermatomes and myotomes Flashcards

1
Q

How many pairs of somites

A

34-35 pairs of somites (Day 30)

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2
Q

Sclerotome

A

Differentiated somite
Ventral
Gives rise to vertebrae and ribs

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3
Q

Dermatomyotome

A

Differentiated somite
Dorsal
Forms the dermis - dermatome
Forms the muscle - myotome

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4
Q

Why does the skin and muscle have the same common spinal nerve supply

A

Derived from the same dermatomyotome

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5
Q

Dermatome

A

Area of skin that is supplied by a single spinal nerve

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6
Q

T4/T5

A

Nipples

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7
Q

T10

A

Umbilicus

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8
Q

L1

A

Groin

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9
Q

Posterior (dorsal) rami

A

After emerging from the intervertebral foramina each nerve root divides into rami

Into medial and lateral branches that supply the skin and deep muscles of the back in a segmental manner

Each dorsal ramus supplies a narrow strip of muscle and skin in line with the intervertebral foramen

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10
Q

Anterior (ventral) rami

A

Complicated distribution

Segmental for the skin and muscle of the trunk

Supply both the anterior (ventral) and posterior (dorsal) skin of the upper and lower limb

C5-T1 - upper limbs (brachial plexus)

L1- S5 - lower limbs (lumbosacral plexus)

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11
Q

C5 - T1

A

Brachial plexus
Upper limbs
No cutaneous distribution on the trunk

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12
Q

L1-S5

A

Lumbosacral plexus

Lower limbs

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13
Q

Adjacent dermatomes in anterior trunk

A

C4 and T2

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14
Q

Functional overlap

A

Overlap between adjacent dermatomes

When a spinal nerve is damaged, the area that loses sensation (anaesthesia) is smaller than expected due to the overlap

Overlap does not extend across an axial line

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15
Q

Hilton’s Law

A

Nerve supplying the joint capsule also supplies th muscles moving the joint and the overlying skin

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16
Q

Neural level (clinical)

A

Lowest level of fully intact sensation and motor function

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17
Q

What does the neural tube consist of

A

Precursor cells for the nervous system

18
Q

Neurone

A

Electrically excitable cell that receives, processes and transmits information via chemical and electrical signals

19
Q

Nerve

A

Enclosed bundle of axons and associated cell bodies e.g Schwann cells in the peripheral nervous system

20
Q

Endoneurium

A

Encloses each axon
Made of glycocalyx and a collagen mesh
Contains endoneurial fluid
Prevents certain molecules from the blood crossing

21
Q

Nerve irritation or injury

A

Endoneurial fluid increases

Oedema detected by MRI

22
Q

Fascicles

A

Bundles of axons enclosed by perineurium

23
Q

Perineurium

A

Covers fascicles

24
Q

Epineurium

A

Covers group of fascicles

Contains nerve blood supply- vasa nervorum

25
Q

Spinal nerve

A

Mixed nerve

  • motor
  • sensory
  • autonomic signals

Exit vertebrae via intervertebral foramina

26
Q

Dorsal nerve root

A

Afferent

Sensory fibres from the sensory receptors towards the spinal cord

27
Q

Ventral nerve root

A

EFFERENT

Carries motor or autonomic fibres that are leaving the spinal cord

28
Q

Spinal cord

A

Origin- inferior margin of the medulla oblongata (base of brain stem)

Up to L1/L2 level - Conus Medullaris

29
Q

Cauda Equina

A

Continuation of spinal cord after L2

30
Q

Where do the cervical spinal roots emerge from in relation to the cervical vertebrae

A

7 vertebrae and 8 nerves

First 7 cervical spinal roots run above the vertebrae
The 8th cervical spinal root runs below C7 (C7/T1)

31
Q

Where does the 5th sacral and 1st coccygeus nerve root exit from

A

Sacral hiatus

32
Q

After the spinal nerve exits the intervertebral foramen, what does it do?

A

Splits into:

  • Dorsal rami
  • Ventral rami
  • Meningeal branch
  • receives grey ramus communicans
33
Q

Meningeal branch

A

Supplies the:

  • vertebrae
  • vertebral ligaments
  • blood vessels
  • meninges
34
Q

Grey ramus communicans

A
  • Joins spinal nerve once exits intervertebral foramen
  • From adjacent paravertebral ganglion of the sympathetic trunk
  • Contains postganglionic nerve fibres of ANS (unmyelinated)
35
Q

Axial line

A

Junction of 2 dermatomes supplied from discontinuous spinal levels

36
Q

Axial borders

A

At the cephalic and caudal margins of the limb bud

Mark the border of the anterior and posterior compartments of the limb

37
Q

Preaxial

A

Upper limb - Rotates and lies laterally (thumb is lateral)

Lower limb - Rotates and lies medially (Big toe is medial)

38
Q

Peripheral nerves

A

Contain different contributions of axons from different spinal nerves

Map pain

39
Q

Myotomes

A

Group of muscles supplied by a single spinal nerve

40
Q

Motor unit

A

Motor neurone and skeletal muscle fibre it innervates

MSK (28 decks)

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