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Organisation of the Body: Gross Anatomy > Nerve supply of the limbs > Flashcards

Nerve supply of the limbs Flashcards

1
Q

Cross sectional structure of the spinal cord

A
  • central region of grey matter surrounded by white matter
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2
Q

Function of white matter

A

arranged in columns containing the nerves containing the brain and spinal cord

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3
Q

Structure of grey matter

A
  • H shape around a central canal

- grey matter broadly divided into two dorsal horns and two ventral horns (posterior and anterior respectively)

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4
Q

What are the dorsal and ventral roots?

A

Pairs of spinal nerves each formed by the fusion of nerve segments knows as the ventral and dorsal roots

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5
Q

What are the rami?

A

The dorsal root, containing sensory information and the ventral root containing motor, join together and then branch off to form the ventral and dorsal rami, each with a mixture of nerves

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6
Q

The posterior (dorsal) ramus structure and function

A

Supplies muscles and sensation to the back- extensors of spine and overlying skin

The dorsal ramus of each spinal nerve travels backward, apart from C1, L4,L5 and coccygeal

Each posterior ramus innervates a narrow strip of skin and muscle along the back, more or less at the level at which it leaves the spinal nerve

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7
Q

The anterior (ventral) ramus structure and function

A
  • supply anterograde-lateral parts of the trunk and the limbs
  • anger than dorsal rami
  • in thoracic region, each ventral ramus supplies a narrow strip of muscle and skin along the sides, chests, ribs and abdominal wall- refereed to as intercostal nerves
  • in regions other than thoracic, the nerves from different rami combine to form plexuses
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8
Q

What are plexuses?

A

A network of tangled nerves from different ventral rami, thus containing several spina; nerves

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9
Q

What is the benefit of nerve plexuses?

A

Fibres from each ventral ramus travels along different routes so that each limb muscle receives innervation from several spinal nerves, thus there is a back up plan in case of injury

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10
Q

What is the brachial plexus?

A

Group of nerve fibres that gets its contribution from the transitional area from neck into axilla, between C5-T1

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11
Q

Brachial plexus function

A

Provides almost all the innervation of the upper limb, including the back and scapular muscles that control the limb

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12
Q

5 stages in a plexus

A

root-trunk-division-cord-terminal

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13
Q

5 major nerves in the arm + their roots

A

Musculocutaneous- C5- C7

Axillary- C5-C6

Radial- C5-T1

Median- C5-T1

Ulnar- C8, T1

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14
Q

Lumbosacral plexus function and roots

A

L1-L4 is lumbar plexus and sacral is L4-S5

Lumbar innervates the anterior thigh, abnormal wall and iliopsoas muscle

Sacral innervates buttocks, pelvis, perineum and lower limb, apart from anterior and medial thigh

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15
Q

5 major nerves in the leg + their roots

A

Obturator L2-L4

femoral- L2-L4

sciatic- L4-S3

tibial- L4-S3

common fibular- L4-S2

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16
Q

How are sensory nerves organised?

A

Afferent nerve fibres from a single dorsal root of spinal nerve innervate a specific area of skin called the dermatome

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17
Q

Dermatome structure

A

Like stacks of discs forming a human

each supplied by a different spinal nerve

dermatomes run longitudinally along the limbs

Slight overlap between dermatomes

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18
Q

Function of dermatome + clinical significance

A

sensory region- allow for cutaneous innervation

If a symptom appears to follow the dermatome, such as a rash, there may indicate a pathology that involves the related nerve root

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19
Q

How are the spinal nerves distributed in the dermatome?

A

Ventral ramus supplies anterior aspect whereas dorsal ramus supplies posterior

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20
Q

What damage could occur to a dermatome?

A

entrapment or damage of a spinal nerve of spinal cord segment

e.g unilateral pain in an S1 dermatome may occur due to the compression of the S1 nerve as a result of disc herniation

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21
Q

Myotome definition

A

Unilateral portion of skeletal muscle receiving innervation from a single spinal nerve

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22
Q

Explain how a myotome is defined

A

Each region of muscle often receives innervation from many spinal nerves, thus each muscle is organised using different myotomes.

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23
Q

Clinical importance of a myotome

A

muscle weakness in a specific myotome territory indicates a lesion at that spinal segment or to that spinal nerve

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24
Q

Do dermatomes and myotomes occupy the same region?

A

No, dermatomes and myotomes of the same segmental level do not necessarily overlap spatially

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25
Q

myotatic reflex definition

A

A muscle contractual in response to stretching within a muscle

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26
Q

Monosynaptic reflex

A

a stretch reflex that provides automatic regulation of a skeletal muscle length, whereby a signal entering the spinal cord arises from a change in muscle length or velocity

27
Q

How does a myotatic reflex work?

A

Muscle spindle structures, whose extrafusal muscle fibres lie parallel to the muscle, sense changes in length and velocity.

Eventually causes an action potential in the alpha motor neurone causing the fibres to contract and thus resist the stretching

28
Q

Explain anatomical basis of biceps reflex

A

Examines the function of the C5/C6 reflex arc

Tendon hammer used to knock the cubital fossa in which the biceps brachii tendon resides

Depresses the muscle spindle, mainly associated with C5 than C6, due to the roots of the musculocutaneous nerve

29
Q

Biceps reflex process

A

Arm is extended, tendon hammer used to strike the examiner’s fingers placed on the biceps tendon

30
Q

Biceps Reflex types and clinical relevance

A

Strong contraction- brisk reflex, weak or absent- diminished

31
Q

Knee jerk reflex process

A

Muscle in neutral position, patellar tendon struck with reflex hammer just bellow the patella

Stretches the muscle spindle of the quadriceps muscle- causes leg to kick

32
Q

Explain anatomical basis of knee jerk

A

Examines the function of the L3 spinal nerve- femoral nerve

33
Q

Clinical relevance

A

Absence or decrease- Westphal’s sign

Multiple oscillations (pendular reflex) - cerebellar disease

exaggerated deep tendon reflexes- hyperthyroidism

34
Q

What are both these an example of ? + stages

A

Reflex arc

  1. Spindle muscles sense changes in length and velocity
  2. impulse carried by afferent sensory neurone from the muscle to the spinal cord
  3. action potential carried to the dorsal root ganglion
  4. action potential carried by efferent motor neurones from the ventral root of the spinal cord to the muscle does the alpha motor neurone
  5. synapses on the extrafusal muscle spindle fibres, causing contraction
35
Q

Two types of plexus + what they innervate

A

autonomic- thorax, abdomen and pelvis- blood vessels and viscera

somatic- limbs- skin, muscle, bone

36
Q

Where are the trunks of the brachial plexus found?

A

between the scalene muscle and clavicle

37
Q

Different trunks and their roots

A

Upper- C5,C6

Median- C7

Lower- C8, T1

38
Q

How does each trunk divide + what they innervate?

A

Each trunk forms an anterior and posterior division

anterior divisions will supply anterior flexor compartments of the rubber limb

posterior divisions will innervate the posterior compartments of the upper limn

39
Q

What do the divisions form?

A

Cords

40
Q

How are they named?

A

Named relative to the axillary artery- li with the axillary arteries and vein surrounded by the axillary sheath

41
Q

3 cords + divisions + trunks

A

posterior- all posterior divisions of all trunks

lateral cord- anterior division of upper and middle trunks

medial cord- anterior division of lower trunk

42
Q

What are the branches?

A

major nerves supplying the upper limb

43
Q

Musculocutaneous nerve origin, location and function

A
  • C5,C6- upper trunk- terminal branches of lateral and medial cord

Passes anteriorly to supple the anterior muscle compartment of the arm

supplies the coracobrachialis, biceps brachii and brachialis muscles

Elbow and shoulder flexion, forearm supination

sensory nerve which supplies skin of the lateral forearm

44
Q

median nerve origin, location and function

A

C5-T1

  • at cubital fossa, nerve lies medial to brachial artery
  • passes into the forearm and at the wrist passes through the carpal tunnel and enters the palm of the hand
  • anterior compartment of the forearm and hand and skin over the lateral aspect of hand
  • innervates wrist, finger, thumb flexion
  • thenar muscle group- abduction, flexion and opposition of thumb
45
Q

Ulnar nerve origin, location and function

A

C8- T1

  • lies medial to brachial artery, passes between medial epicondyle of the humorous in the cubital tunnel
  • motor to muscle of anteromedial aspect of the forearm and hand
46
Q

Radial, nerve origin, location and function

A

C5-T1

  • posterior, extensor, compartments of the arm and forearm
  • supplies no muscle in the hand but does innervate the skin of the dorsum of the hand
  • elbow extension due to the triceps brachii, wrist extension
47
Q

Axillary nerve, origin, location and function

A

C5-C6

  • Innervates deltoid and teres minor muscles, shoulder joint and skin overlying deltoid muscle - regimental badge
48
Q

Lumbar plexus roots

A

L1-part of L4

49
Q

Where is the lumbar plexus located?

A

Deep two psoas major muscle

50
Q

lumbar sacral trunk roots

A

L4, ventral ramus L5

51
Q

Sacral plexus roots

A

S1,S2,S3

52
Q

Sacral plexus location

A

anterior to piriformis muscle

53
Q

Where do the branches pass?

A

greater sciatic foramen to the gluteal region and lower limb

54
Q

Femoral nerve, origin, location and function

A

-L2,L3,L4

innervates muscles of the anterior compartment of the thigh- quadriceps femurs group, sartorius and the skin overlying he anterior thigh

  • carries sensory information from the knee and hip joint
  • lateral to psoas major, enters thigh behind inguinal ligament
  • lies lateral to femoral blood vessels
  • in the femoral triangle
55
Q

Obturator nerve, origin, location and function

A

L2, L3, L4

  • emerges from medial border of psoas major muscle
  • follows the curve of lateral pelvic wall
  • passes through the obturator foramen of the pelvis t

-enter the medial compartment of the thigh where it supplies adductor muscles and skin overlying the medial aspect of the thigh

56
Q

Sciatic nerve, origin, location and function

A

L4-S3

  • emerges from pelvis via the greater sciatic foramen and passes midway between the greater tech-anger and ischial tuberosity
  • supplies all leg and foot muscles
57
Q

What does the sciatic nerve divide into + where?

A

Common perineal and tibial nerve at about the mid-thigh level, above the popliteal fossa

58
Q

Tibial nerve, origin, location and function

A

L4-S3

  • passes into leg to run deep to the soleus muscle
  • innervates muscles in posterior compartment of the leg
  • responsible for plantar flexion and inversion
  • enters sole of foot behind medial mallows
59
Q

What does the tibial nerve divide into + where?

A

medial and lateral plantar nerves

60
Q

Common perineal nerve, origin, location and function

A

L4-S2

  • curves posteriorly around the neck of the fibula
  • supply anterior and lateral compartment of the leg
61
Q

What does the common perineal nerve divide into + where?

A

Superficial peroneal nerve- supplies muscles in lateral compartment, and anterolateral distal 1/3 of the leg and dorsal surface of foot

deep perineal nerve- anterior compartment

62
Q

Different ways in which a nerve is damaged explained

A

neurapraxia- nerve is bruised or squashed but the outer layer and inner fibres are still in tact- works properly again after a few weeks

axonotmesis- nerve is crushed, inner nerve fibres damaged but outer layer in tact

neurotmesis- both layers are cut

63
Q

Main effects of damage

A

loss of sensation, loss of dexterity or paralysis

64
Q

Examples of common nerve injuries, explained

A

Erb palsy- upper trunk of brachial plexus caused by excessive lateral flexion of the neck- causes weak biceps etc

axillary nerve injury- anterior shoulder isolation- paralysis of deleted muscle- impaired arm abduction

carpal tunnel syndrome- median nerve trapped as it travels through the wrist at the carpal tunnel - causes pain, numbness and tingling

Organisation of the Body: Gross Anatomy (9 decks)

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