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MSK > week 2 > Flashcards

week 2 Flashcards

1
Q

Briefly explain the formation of the dermatomes and myotomes embryologically

A

In the fourth week the dermamyotome which airses from the dorsal half of somites differentiates into the dermatomes (becomes the dermis) and the myotomes (becomes the muscle)

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2
Q

Define what a dermatome is

A

An area of skin which is supplied by a single spinal nerve

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3
Q

How many pairs of spinal nerves are there?

A

31

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4
Q

A spinal nerve is a mixed nerve consisting of sensory and motor fibres. Does the Dorsal root contain cell bodies of motor or sensroy fibres?

A

sensory

ventral contains motor

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5
Q

What does the ventral part of the somites become?

A

sclerotom which then becomes the verterbae and ribs

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6
Q

Where in the vertebrae do the spinal nerves run?

A

Through the interverterbal foramen

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7
Q

At what level does the spinal cord terminate?

A

L2 (starts at the level of the medulla oblongata)

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8
Q

All cervical spinal nerves exit _____ their corresponding verterbae (apart from C8 which enters at C7/T1. The rest enter _____ their corresponding vertebrae

A

above

below

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9
Q

At what level does the cauda equina run to and from?

A

L2-S5

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10
Q

After emerging through the interverterbal foramin the spinal nerves split into ventral and dorsal rami, which sipply the upper and lower limbs skin and muscles?

A

ventral

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11
Q

What then does the dorsal rami supply?

A

The skin of the back in a segmental manner

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12
Q

If a single spinal nerve is damaged why is the area of parasthesia smaller than expected?

A

Because there is functional overlap between adjacent dermatomes, i.e. areas are innervated by more than one spinal nerve

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13
Q

Where does functional overlap not extend across?

A

axial lines - the junction of two dermatomes supplied by discountinuous spinal levels

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14
Q

where do the axial lines run on the limbs?

A

Middle of anterior and posterior compartments

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15
Q

Axial borders are different to axial lines; they separate compartments rather than axial lines which mark thejunection of dermatomes of discontinuous levels. Each limb has a pre and post axial border.. Pre-axial borders relate to the borders which are rotated i.e. pre-axial border in the arm is externally rotated and pre-axial border in the leg is internally rotated. State the pre and post axial borders in the limbs

A

Arms

  • Pre-axial border = cephalic vein
  • Post-axial border = basilic vein

Legs
Pre-axial border = Long saphenous vein (runs in front of medial malleolus)
Post-axial border = short saphenous vein (runs posterior to lateral malleolus)

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16
Q

What is a myotome/

A

A group of muscles supplied by a single spinal nerve

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17
Q

What is meant by a ‘neural level’?

A

The lowest level of fully intact sensation and motor function

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18
Q

State the myotomes

A

C5 - shoulder abduction and external rotation
C6 - elbox flexion, wrist extension and supination
C7 - Elbox extension. wrist flexion, pronation
C8 - finger flexion and extension
T1 - finger abduction and adduction
L2 - Hip flexion
L3 - knee extension
L4 - ankle dorsiflexion
L5 - great toe extension
S1 - ankle plantar flexion
S2 - great toe flexion

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19
Q

How many coccygeal veterbrae are there? How many sacral vertebrae are there?

A

Coccygeal - 4
Sacral - 5
Separately fused (sacral and coccygeal)

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20
Q

Why is the thoracic spine less mobile as compared to the cerival and lumbar verterbae?

A

The verterbae are connected to the ribs and sternum

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21
Q

Why do the vertebral bodies increase in size inferiorly?

A

Because they have to take more compressive forces (more body weight)

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22
Q

What are three roles of the spinal column?

A
  • Posture and locomtion
  • Protect the spinal cord
  • Support body weight
  • Contains bone marrow - site of haemopoiesis
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23
Q

Lamina forms an ‘L’ with the spinous process and pedicle forms a ‘P’ with the vertebral body

A

T

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24
Q

What are the functions of the spinous and transverse processes?

A

Provide attachments for muscles and ligaments

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25
Q

Facet joints are formed between adjacent superior and inferior articular processes - what is their function?

A

Prevents the anterior-posterior displacement of the verterbrae

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26
Q

What are the major movements permitted at the lumbar spine?

A

Flexion and extension

27
Q

What is the name and function of the outer region of interverterbal discs?

What is the name and function of the inner region of intervertebral discs?

A

Annulus fibrosis - acts as a shock absorber (made of type 1 collagen)

Nucleus pulposus - more gelatinous and elastic. Allows it to withstand pressure

28
Q

the anterior and posterior longitudinal ligaments are continuous anteriorly and posteriorly with the vertebral bodies. What are their actions?

A

anterior - prevents hyperextension
posterior - prevents hyperflexion - llso prevents posterior disc prolapse so it occurs slightly laterally (paracentral disc prolapse)

29
Q

Where does the ligamentum flavum run?

A

Between lamina of adjacent vertebrate - prevents hyperflexion

30
Q

What are the actions of almost all the spine ligaments?

A

prevent hyperflexion of the spine

31
Q

what is the conus medullaris?

A

Tapered, lower end of he spinal cord - beginning of the cauda equina

32
Q

what is the filum terminale?

A

A continuation of the pia mater (a meninge), it surrounds the nerves forming the cauda equina

33
Q

What is a kyphosis?

A

A PRIMARY curvature of the spine (C shaped) - concave anteriorly - arching out backward. throughout life. There are two - thoracic and saccrococcygeal

34
Q

Lordosis’ arch out forward (posterior flexion, concave posteriorly) These are secondary curvatures. Two develop in life, when are these?

A

When the baby first lifts its head (cervical lordosis). When the child begins to walk (lumbar lordosis)

35
Q

How can you account for the loss of height seen in older people?

A

The nucleus pulposus undergoes degeneratino and becomes dehydrated, thus compression fractures can happen more easily with age too

36
Q

What are somre risk factors for ‘mechanical back pain’ which is pain when the spine is loaded and worsens with exercise

A

Obesity, poor posture, poor core muscles, sedentary lifestyle, poor manual handling

37
Q

Why do we see patients getting pain in the spine as they age?

A

Loss of heigh of the vertebrae due to dehydration of the nucleus pulposus mans that spinal nerves can be compressed resulting in pain. Osteophytes also form due to the structural changes and can cause osteoporosis.

38
Q

Explain what happens in an intervertebral disc herniation

A

Discs degenerate and bulge with age, they hten prolapse which is here the nucleus pulposus impinges a little on the spinal canal but is still contained within the annulus. Extrusion then occurs which is where the nucleus pulposus bursts through the annulus but is still within the disc space. And lastly sequestration - the nucleus leaves the disc space and enters the spinal canal

39
Q

In a paracentral herniation (most common) of the L4/L5 disc, which spinal nerve will be affected, due to compression,what about if this was a far lateral herniation/

A

Paracentral - L5

Far lateral - L4

40
Q

Sciatica is the name given to pain caused by compression of the one or more of the nerve roots which contribute to the sciatic nerve (L4-S3). Be able to distinguish where potential pain/parasthesia may be felt using your dermatome maps

A

T

41
Q

What are the nerve roots of the lumbosacral plexus?

A

L1-S3 CHECK THIS

42
Q

Cauda equina syndrome is when a ‘canal-filling’ disc compresses the lumbar and sacral roots of the spinal cord. What can cause this?

A

Disc prolapse/spinal infection/tumours

43
Q

What are the five red flag symptoms of cauda equina syndrome?

A

Bilateral sciatica/perianal numbness/painless retention of urine/urinary or fecal incontinence/erectile dysfunction
Can be remembered by ‘BUPPE’

44
Q

How do you treat cauda equina syndrome? What are the consequences if left untreated?

A

Surgical decompression within 48 hours. If not self-catheterisation/incontinence/loss of sensation and lower limb weakness requiring a wheelchair

45
Q

What is spinal canal stenosis and who does it most commonly affect?

A

Abnormal narrowing of the spinal canal, tends to affect the elderly as a combination of facet joint osteoarthritis, disc bulging and ligamentum flavum hypertrophy.

46
Q

What are some symptoms of spinal canal stenosis?

A

Discomfort whilst standing/pain in the limbs or neck depending on where it is/numbness and or weakness at or below the level of stenosis

47
Q

What is spondylolisthesis?

A

anterior displacement of the verterba above onto the vertebra below

48
Q

What are some causes and symptoms of spondylolisthesis (note - you should be able to spot this on an x-ray)

A

Cause - trauma/congenital/degenerative/infection/surgery

symptoms - neurogenic claudication (nerve pain like pins and needles) and sciatica/lower back pain depending on where it is

49
Q

Where would we administer a lumbar puncture and why?

A

Between the spinous processes of L3 and L4 (can be found at highest points of iliac crest. At this point we cannot damage the spinal cord - used to collect CSF. Go over is higher lor lower bad?

50
Q

How are peripheral nerves formed?

A

The axons different spinal nerves form plexi which then can join into and form different peripheral nerves

51
Q

What spinal rami supply the deep muscles and skin of the dorsal trunk?

A

dorsal rami

52
Q

Remember if a patients is stabbed and damage is done to a peripheral nerve they will have anasthesia in the cutaneous distribution of the nerve but also paralysis in muscles DISTAL to the site of injury T/F

A

T

53
Q

What part of the vertebrae do the inferior and superior articular processes project from?

A

Lamina

54
Q

What are the nerve roots and function of the cauda equina?

A

L2-S5 - supply the pelvic organs (e.g. bladder) and lower limbs

55
Q

What is the filum terminale?

A

a continuation of the pia mater from the conus medullaris of the spinal cord to the first segment of the coccyx. It is approximately 20cm in length and gives longitudinal support to the spinal cord.

56
Q

The cervical and lumbar lordosis mean that there are two kyphosis’ in the grown up, where are these?

A

thoracic and sacral

57
Q

Why is the shortening of intervertebral disc height and formation of osteophytes in the spine perceived as painful?

A

The meningeal branch of the spinal nerves travels through the intervertebral foramens to supply the vertebrae, this is compressed by this and the increased loading on the facet joints. Eventually it can compress the spinal nerves themselves

58
Q

Whick kind of disc herniation is most likely to cause cauda equina syndrome?

A

central (goes striaght back into spinal cord)

59
Q

what is parasthesia?

A

pins and needles sensation in skin, chiefly the result of pressure on peripheral nerves

60
Q

What is a motor unit?

A

A single motor neuron and the skeletal muscle fibres it innervates

61
Q

What 4 elements contribute to the stability and mobility of the vertebral column?

A

Strength and compressibility of the intervertebral discs
Tone of strong back muscles
Resistance of ligaments
Shape and orientation of the facet joints

62
Q

What landmark is important in demarkating the plane for a lumbar puncture?

A

The highest point of the iliac crests

63
Q

State the four stages of disc herniation and explain

A

Degeneration - discs dehydrate and bulge
Prolapse - Nucleus protrudes a little but is still contained within the annulus
Extrusion - Nucleus breaks through the annulus but is still contained within the disc space
Sequestration - Nucleus exits the disc space and protrudes directly into the canal

64
Q

Why is S1 the nerve root likely damaged in a paracentral herniation of the L5/S1 disc?

A

Because this is the traversing root and most likely damaged in this form of herniation

MSK (11 decks)

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