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MSK > 16 - Axilla and Brachial Plexus > Flashcards

16 - Axilla and Brachial Plexus Flashcards

1
Q

What do I need to know?

A
  1. Axilla boundaries, contents and relative position
  2. BP
  3. Functional relationship between anterior and posterior divisions of BP and flexor and extensor aspects of the limb
  4. Relation of the BP to the brachial artery and vein
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2
Q

What is the axilla?

A

A space between the upper arm and side of the upper chest. Is a truncated pyramid.

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3
Q

What are the borders of the apex of the axilla?

A

Medially: Outer border of 1st rib
Anteriorly: Clavicle
Posteriorly: Superior border of scapula

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4
Q

What are the borders of the base of the axilla? I.e. the armpit

A

Posterior Axillary Fold: latissimus dorsi
Anterior Axillary Fold: Pec Major
Medial Border: Serratus Anterior
Lateral Border: Medial Humerus

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5
Q

What forms the anterior and posterior WALLS of the axilla?

A

Posterior wall: Subscapularis

Anterior wall: Pectoralis Major and Minor

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6
Q

What are the contents of the axilla?

A

The CORDS and BRANCHES of the BP, axillary artery and vein, lymph nodes, lymphatics and fat

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7
Q

How many groups of lymph nodes are there in the axilla?

A

5

  1. Brachial (drains arm)
  2. Pectoral (drains most of breast so important in spread of carcinoma)
  3. Posterior/Subscapular (drains upper trunk posteriorly)
  4. Central (receives from OTHER lymph node groups)
  5. Apical (receives from ALL other groups and drains into the thoracic duct or right lymphatic trunk)
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8
Q

How are the limbs innervated?

A

Via the brachial and lumbosacral plexuses

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9
Q

What is the brachial plexus formed by?

A

The Ventral Rami of spinal nerves C5-T1

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10
Q

How is the BP divided?

A

Roots, Trunks, Divisons (A/P), Cords, Terminal Branches (2)

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11
Q

What is the relation between the divisions and flexor/extensor compartments of the upper limb?

A

There is an anterior and posterior division from each trunk. The anterior divisions will eventually supply the flexor compartments of the upper limb (Lateral cord and medial cord) and the posterior divisions will supply the extensor compartments (posterior cord)

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12
Q

Where do the BP roots arise form?

A

From between scalenus anterior and scalenus medius

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13
Q

Where do the trunks of the BP lie?

A

Lower part of the posterior triangle of the neck

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14
Q

Which parts of the BP are supraclavicular and which are infraclavicular?

A

The roots and trunks are supraclavicular (between scalenus anterior and medius, and lower posterior triangle of the neck), divisions are subclavicular and cords and branches are infraclavicular

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15
Q

Where do the divisions of the BP lie?

A

Behind the clavicle

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16
Q

Where are the cords of the BP formed?

A

At the outer border of the 1st rib and enter the apex of the axilla with the axillary artery, vein

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17
Q

How are the BP cords named?

A

With respect to their spatial position to the axillary artery (medial, lateral and posterior)

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18
Q

Are the terminal branches motor or sensory?

A

Both. They are mixed.

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19
Q

What are the terminal branches of each cord?

A

Lateral: Musculocutaneous Nerve and lateral head of Median Nerve
Posterior: Radial Nerve and Axillary Nerve
Medial: Ulnar Nerve and medial head of Median Nerve

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20
Q

What is the difference between a dermatome and a cutaneous nerve distribution?

A

Dermatome: Area of skin supplied by a particular spinal nerve. A dermatome may be supplied by SEVERAL cutaneous nerves, and the distribution of a cutaneous nerve may not be restricted to a single dermatome. Symptoms relating to a specific dermatome (parasthesia, pain) is serious and may indicate spinal involvement rather than a single cutaneous nerve

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21
Q

How does the BP, Axillary artery and Axillary Vein enter the axilla?

A

> Enter medially across the 1st rib
The Brachial Plexus and Axillary artery run more posteriorly than the vein, in between the anterior and middle scalene muscles.
The Axillary Vein is the most anterior and passes anterior to the anterior scalene muscle, posterior to the clavicle

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22
Q

Why is the axillary vein more anterior?

A

Ensures it doesn’t get compressed by the anterior and middle scalene muscles

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23
Q

Anterior Wall of Axilla?

A

Clavicle, deep fascia of subclavius, costocoracoid ligament, pectoralis minor (and major anteriorly), suspensory ligament of the axilla

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24
Q

Posterior Wall of the Axilla?

A

Supraspinatus, Subscapularis, Teres MAJOR, Latissimus Dorsi (a bit of scapula)

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25
Q

Lateral Wall of Axilla?

A

Intertubercular Groove of Anterior Humerus (biceps tendon sits in here and triceps is posterior)

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26
Q

Medial Wall of Axilla?

A

(only see in transverse section)

Serratus Anterior and Lateral Thoracic Wall

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27
Q

Base of Axilla?

A

Axillary Fascia (anteriorly the suspensory ligament pulls this up to make the ‘pit’ of the armpit)

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28
Q

What is the suspensory ligament and costocoracoid ligament called together?

A

Clavipectoral Fascia

29
Q

The axilla acts as a …

A

passage for all BVs and nerves to the free limb AND supplies the walls of the axilla

30
Q

How does the BP arise?

A

Spinal Cord (CNS) > Rootlets > Dorsal and Ventral Roots (OF the spinal cord) > Spinal Nerve (PNS - leaving the spinal cord/vertebral canal) > Anterior Rami (are the roots of the PLEXUS)

31
Q

What forms the roots of the brachial plexus?

A

The anterior rami of SPINAL NERVES C5 > T1

32
Q

Are spinal nerve roots mixed? Are plexus roots mixed?

A

Spinal Nerve Roots = Dorsal/Ventral (sensory/motor)

Plexus Roots = Mixed motor and sensory

33
Q

When C4 also contributes to BP it is called…

A

Pre-fixed Plexus

34
Q

When T2 also contributes to BP it is called…

A

Post-fixed Plexus (don’t get BOTH pre and post-fixed)

35
Q

What nerves come directly off of the trunks?

A

2 come off of the superior trunk - nerve to subvlavius and SUPRASCAPULAR

36
Q

The lateral cord directly gives off…

A

Lateral pectoral nerve

37
Q

Lateral cord terminates to …

A

Musculocutaneous Nerve and lateral head of Median Nerve

38
Q

Posterior cord gives off …

A

Upper Subscapular, Thoracodorsal, Lower Subscapular Nerves

39
Q

Posterior cord terminates to

A

Axillary nerve and Radial Nerve

40
Q

Medial Nerve gives off

A

Medial cutaneous nerve of forearm and arm and medial pectoral nerve

41
Q

C5,C6,C7 each contribute to the

A

Long Thoracic Nerve

42
Q

C5 directly give off …

A

Dorsal Scapular Nerve

43
Q

Dorsal Scapular Nerve

A

Given off by C5 and supplies both Rhomboids and Levator Scapulae

44
Q

Suprascapular Nerve

A

Given off by superior trunk and supplies both supra/infraspinatus

45
Q

Lateral Pectoral Nerve

A

Given off by lateral cord and supplies only pectoralis major

46
Q

Musculocutaneous Nerve

A
  • lateral cord
  • motor supplies anterior arm (biceps/coracobrachialis/brachialis)
  • becomes lateral cutaneous nerve of the forearm
47
Q

Median Nerve

A
  • lateral and medial cords
  • lateral 3/4 muscles of anterior forearm (PT, FCR, PL, FDS, FDP, FPL, PQ)
  • 1/4 lateral hand muscles (thenar muscles and lateral 2 lumbricals)
  • skin of palm lateral 3.5 digits

> means that high neck injuries can manifest as hand numbness

48
Q

Ulnar Nerve

A
  • medial cord
  • 1/4 anterior muscles of forearm (FCU, FDP)
  • 3/4 hand muscles (hypothenar muscles, FPB, PB, AP, dorsal and palmar interossei, 3/4 lumbricals)
  • 1.5 medial fingers sensory
49
Q

Axillary Nerve

A
  • posterior cord
  • teres minor and deltoid
  • lateral shoulder sensory
    (intermuscular injection into deltoid that is too low and deep may injure this nerve
50
Q

Radial Nerve

A
  • posterior cord
  • posterior arm and forearm
    (triceps, anconeus, brachioradialis, ECRL, ECRB, ED, EDM, ECU, supinator, EPL, EI, EPB, APL)
  • sensory area is everything left on posterior
51
Q

Are there muscles in the posterior hand?

A

no

52
Q

Describe the course of the axillary artery

A

Subclavian A > 1st rib > Axillary Artery > Superior Teres major > Brachial Artery

53
Q

How is the artery divided into 3 parts?

A

1st rib > 1 > superior border pec minor > 2 > inferior border pec minor > 3 > superior border teres major

54
Q

What are the arteries?

A
  1. Subclavian > suprascapular A and dorsal scapular A (deep and superficial)
  2. Superior Thoracic Artery
  3. Thoracoacromial Artery (deltoid, pectoral, acromial branches)
    Lateral Thoracic Artery
  4. Subscapular Artery > Thoracodorsal A and Circumflex Scapular A
    Anterior and Posterior Circumflex Humeral Arteries
55
Q

Suprascapular A

A

Infra/supraspinatus

56
Q

Dorsal Scapular A

A 
Deep = Rhomboids
Superficial = Trapezius
57
Q

Superior Thoracic A

A

Upper medial wall

58
Q

Thoracoacromial A

A

Pectoral, deltoid, acromial branches

> anterior wall

59
Q

Lateral Thoracic A

A

Lower medial wall

60
Q

Subscapular A

A

> posterior wall

> Gives off circumflex scapular A (back of scapula) and thoracodorsal A (lower posterior wall)

61
Q

Anterior and posterior circumflex humeral A

A

Lateral Border

62
Q

How to remember the arteries of the axilla?

A 
Stop That Laughing Samantha Heape
> Superior Thoracic
> Thoracoacromial
> Lateral Thoracic
> Subscapular (thoracod. + circumflex scap)
> Humeral circumflex (ant and post)
63
Q

What arteries anastomose at the back of the scapular?

A

Dorsal scapular A, Suprascapular, Circumflex Scapular A

64
Q

What lymph node does 75% of the breast drain into?

A

The PECTORAL node

65
Q

Where does the free limb lymph drain to>

A

Humeral node

66
Q

Describe the flow of lymph

A

Pectoral nodes + humeral nodes + subscapular nodes drain to CENTRAL nodes which drain to apical nodes > subclavian trunk

67
Q

Where are the lymph nodes?

A

In clusters at the corners of the axilla

68
Q

What are sentinel nodes?

A

Is when you put dye in the lymph and the first node to receive drainage from the breast will colour - the sentinel node is usually the pectoral node (occasionally apical)

MSK (29 decks)

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