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Anatomy > Brachial Plexus > Flashcards

Brachial Plexus Flashcards

1
Q

The brachial plexus provides somatomotor and somatosensory innervation to
the

A

upper extremity

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2
Q

The brachial plexus arises from the

A

cervical enlargement of the spinal cord

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3
Q

It is formed by the anterior rami of cervical spinal nerve roots

A

C5-T1

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4
Q

These spinal nerve roots emerge from the — — of cervical
vertebrae and pass between the — of the neck

A

intervertebral foramina
anterior and middle scalene muscles
(interscalene space)

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5
Q

The brachial plexus is made up of the

A

ANTERIOR (VENTRAL) RAMI

of cervical and thoracic spinal nerves (C5 – T1)

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6
Q

Topographically, portions of the brachial plexus (trunks) emerge

A

posterolateral to the sternocleidomastoid muscle in the
lateral neck region, in an area called the posterior triangle, through the interscalene space (between the middle and anterior
scalene muscles) at approximately the level of the cricoid cartilage of the larynx.

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7
Q

The brachial plexus maintains an anatomical relationship with vascular structures emerging from the root of the neck
(subclavian a. and v.) as it travels

A

posterior to the omohyoid muscle and the clavicle

on its way into the axilla

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8
Q

For some surgeries involving the upper extremity, an — — is one example of a
procedure that can be performed as an alternative to general anesthesia

A

interscalene block

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9
Q

Typically guided by ultrasound, local anesthetic agents are injected close to the brachial plexus,
temporarily blocking

A

sensation and motor function to the the upper limb

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10
Q

Knowledge of the anatomical relationships within the — — of the neck is essential to
the safety success of this procedure

A

posterior triangle

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11
Q

Common complication:

A

Accidental partial anesthesia of the diaphragm and temporary respiratory
depression due to proximity of phrenic nerve (C3-C5; cervical plexus) to the anterior scalene m. and
compartmentalization of fascia within the neck

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12
Q

As the brachial plexus travels posterior to the clavicle, it enters the axillary region and travels posterior to the

A

pectoralis minor m.

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13
Q

Here it forms an intimate relationship with the axillary a. such that the artery itself runs

A

in

the middle of the plexus, surrounded by the cords and terminal branches.

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14
Q

The — — and it’s tributaries also seem to “entangle” themselves with
the various branches of the brachial plexus

A

axillary vein

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15
Q

As the brachial plexus runs into the axilla, along with the axillary a. and v., it is surrounded in this
neurovascular bundle by the

A

axillary sheath

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16
Q

Dermatome

A

area of cutaneous sensory innervation supplied by a single spinal nerve

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17
Q

For upper extremity this means brachial plexus (C5-T1), but some areas in the axilla are supplied by

A

lower thoracic spinal nerves (T2-T5)

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18
Q

C4 dermatome

A

Supraclavicular and upper shoulder region

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19
Q

C5 dermatome

A

Upper lateral arm and shoulder

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20
Q

C6 dermatome

A

Posteriolateral arm and lateral forearm

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21
Q

C7 dermatome

A

Middle of forearm and hand

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22
Q

C8 dermatome

A

Posteriomedial forearm and medial hand

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23
Q

T1 dermatome

A

Medial arm

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24
Q

T2-T5 dermatome

A

Axillary region

25
Q

SKIP
This is a MAP of cutaneousspinal nerve distribution in the upper limb, with the corresponding dermatome map
• It includes spinal nerves

A

C4 – T5

26
Q

Note that there is not a — correspondence between named cutaneous nerves and dermatomes. Named nerves
may be comprised of — spinal nerve and thus will span more than one dermatome.

A

1:1

>1

27
Q

As a general rule, an individual named muscle in the limbs is supplied by

A

more than one spinal nerve

28
Q

Anatomically, the term myotome refers to a group of muscles that receive

A

motor innervation from a single spinal nerve

29
Q

Myotomes may —

A

overlap

30
Q

C4 myotomes (motor)

A

Shoulder elevation

31
Q

C5 myotomes (motor)

A

shoulder abduction; elbow flexion

32
Q

C6 myotomes (motor)

A

Elbow flexion; wrist extension

33
Q

C7 myotomes (motor)

A

Elbow extension; wrist flexion

34
Q

C8 myotomes (motor)

A

Thumb and finger extension

35
Q

T1 myotomes (motor)

A

Intrinsic hand muscles

36
Q

T2 myotomes (motor)

A

Intercostal muscles

37
Q

Each of the trunks of the brachial plexus has

(2) division

A

an anterior and a posterior

38
Q

These divisions will contribute to branches

that correspond to

A

anterior parts of the limb

or posterior parts of the limb

39
Q

Innervation of the Upper Limb Follows a — Pattern

A

Compartmentalized

40
Q

ARM (BRACHIUM):
Anterior Compartment
=

A 
Musculocutaneous Nerve
(flexors of elbow joint)
41
Q

ARM (BRACHIUM):
Posterior Compartment
=

A 
Radial Nerve
(extensors of elbow joint)
42
Q

anterior compartment has only

A

anterior division contributions from spinal

nerves

43
Q

posterior compartment has only

A

posterior division contributions from spinal

nerves

44
Q

FOREARM (ANTEBRACHIUM)
and HAND:
Anterior Compartment
=

A

Ulnar & Median Nerves

45
Q

FOREARM (ANTEBRACHIUM)
and HAND:
Posterior Compartment
=

A

Radial Nerve

46
Q 
The shoulder (pectoral girdle) region is 
innervated by
A

nerves that come directly
from the roots, trunks, or cords of the
brachial plexus (mostly)

47
Q

The arm (brachial) region is innervated by

A

the nerves from the medial cord (cutaneous),
the musculocutaneous n. (anterior) and the
radial n. (posterior)

48
Q 
The forearm (antebrachial) region is 
innervated by
A

a branch from the medial cord

cutaneous) , the median and ulnar nerves
(anterior) and the radial n. (posterior

49
Q

The hand receives all motor innervation from
(2), and
sensation from (3)

A

the median and ulnar nerves
median, ulnar and radial
nerves

50
Q

Upper/Superior Trunk Lesion =

A

Erb’s Palsey

51
Q

Erb’s Halsey results from

A

excessive, forceful increase in angle between neck

and shoulder

52
Q

Erb’s Palsey is most common

A

obstetric brachial plexopathy

53
Q

Erb’s Halsey can also occur in adults from a

A

fall onto the shoulder

54
Q

Erbs Palsey

A

Injuries to Superior Trunk (C5 & C6)Upper/Superior Trunk Lesion = Erb’s Palsey
Clinical Presentation:
At the shoulder and elbow:
•Arm will be adducted
•Arm will be internally (medially) rotated at the elbow
•There will be pronation
•There will be extension
This describes the “waiter’s tip”position of the
affected upper limb.

55
Q

Nerve Deficits & Affected Muscles
• C5 Spinal Nerve Root (3)
• C6 Spinal Nerve Root (1)

A

• Axillary nerve (weakness in deltoid and teres
minor)
• Suprascapular nerve (from Superior Trunk-
weakness in supraspinatus and infraspinatus)
• Musculocutaneous nerve (weakness in biceps)

• Radial nerve (weakness in brachioradialis and
supinator, and wrist extensors)

56
Q 
Injuries to the Radial Nerve (C5-T1)
Axillary Region (nerve is injured before it supplies triceps): Clinical Presentation
A

•Improper use of crutches can compress and injure the nerve in the axilla
Clinical Presentation (posterior compartment affected)
•Weakness when trying to push something away with arm
•Difficulty extending the wrist
•Difficulty extending the fingers and opening the hand
•“wrist drop” posture

57
Q

Injuries to the Radial Nerve (C5-T1)

Injury at Spiral Groove of Humerus: Clinical presentation

A

•Compression of the radial nerve along the midshaft of the humerus in certain
positions (“Sleep Palsy”, “Saturday Night Palsy”)
•Humeral fracture at midshaft (spiral groove fracture)
Clinical Presentation
•Difficulty extending the wrist
•Difficulty extending or straightening the fingers and opening the hand
•Triceps retains strength because nerve fibers entering this muscle branch off
proximal to the mid shaft of the humerus
•Also causes “wrist drop” posture

58
Q

Injuries to the Axillary Nerve (C5, C6)
Causes: (3)
Clinical Presentation: (4)

A
  • Fracture to surgical neck of humerus
  • Anterior dislocation of glenohumeral joint
  • Rotator cuff repair surgery
  • Numbness in posterior deltoid region
  • Difficulty abducting arm
  • Diminished lateral rotation of arm
  • Deltoid muscle wasting (prolonged injury)
59
Q

Injuries to the Long Thoracic Nerve (C5, C6, C7)(innervation to the serratus anterior muscles)
Causes: (2)
Clinical Presentation: (2)

A
  • Penetrating wound to the axillary region
  • Surgical removal of axillary lymph nodes
  • cannot raise arms above 90O
  • “winged scapula”

Anatomy (29 decks)

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