Axilla Brachial Plexus and Arm

Question 1

Deep fascia: Brachial

Answer 1

Lateral and medial intermuscular septa attach to the bone
Divide into anterior and posterior compartment
Clinical importance: fascial compartments of the upper limb contain and direct the spread of infection or hemorrhage in the limb - compartment syndrome - cut fascia to release pressure so you don’t damage the nerve - not as common in arm

Question 2

Superficial veins of the upper limb

Answer 2

Cephalic veins (travels laterally)
Basilic vein (travels medially)
Connected by Median cubital vein - where you draw blood from
Both drain in to the axiallary vein

Question 3

Arteries of the upper limb

Answer 3

Subclavian artery
Axillary arters

Question 4

Subclavian artery

Answer 4

arises from the brachicephalic on the right and directly from the arch of the aorta on the left - remember this
Subclavian becomes the axillary artery at the lateral border of the 1st rib

Question 5

Axillary artery branches

Answer 5

First:
1. Superior thoracic artery - to first intercostal space
Second:
1. Thoraco-acromial trunk (acromial branch, clavicular branch, deltoid branch, pectoral branch) - into four additional arteries
2. Lateral thoracic artery - sits away from thoracic wall - give blood to serratus anterior
Third:
1. Subscapular artery (thoracodorsal artery in lattisimus dorsi,) (circumflex scapular artery - triangular space)
2. Anterior humeral circumflex artery - small
3. Posterior humeral circumflex artery - large - in quadrangular space

Question 6

Thoraco-acromial trunk

Answer 6

1. Acromial branch
2. Clavicular branch
3. Deltoid branch
4. Pectoral Branch

Question 7

Brachial plexus Hierarchy

Answer 7

Roots (5): emerge through anterior and middle scalene m.m.
Trunks (3): lie superior to the 1st rib and course with subclavian a.
Divisions (6): split off behind clavicle; anterior and posterior from each trunk
Cords (3): posterior to pectoralis minor m. and related to 2nd part of axillary a. - Don’t tag above the cords
Branches (terminal) (5) continue out
written questions: all fair game

Question 8

How to draw the brachial plexus

Answer 8

3 Y’s
1 M
1 X
1 Back slash
Randy Travis Drinks Cold Beer

Question 9

Divisions

Answer 9

Each trunk divides into a anterior and posterior

Question 10

Musuculocutaneous nerve

Answer 10

Formed from lateral cord
C5-C7 ventral rami contributions
Pierces thru coracobrachialis muscle
- descends between biceps brachii and brachialis mm.
Major nerve of the anterior arm
Continues as lateral cutaneous nerve of arm (innervates skin of lateral forearms)
Muscles and cutaneous

Question 11

Ulnar nerve

Answer 11

Formed from medial cord
C8-T1 ventral rami contributions
Located medial to brachial artery in arm
Run posterior to Medial epicondyle - pinches ulnar nerve - funny bone
Innervates NOTHING in arm or forearm
Runs behind medial epicondyle
Major Nerve of the hand

Question 12

Median Nerve

Answer 12

Formed from 1/2 lateral cord and 1/2 medial cord
C6-T1 ventral rami contributions
Passes medial to arm mm.
Lateral to brachial artery proximally
Distally crosses to medial side of brachial artery
Innervates NOTHING in arm
Major Nerve of the anterior forearm

Question 13

Axillary nerve

Answer 13

Formed from posterior cord
C5-C6 ventral rami contributions
Circles behind humerus in quadrangular space (with posterior circumflex humeral artery)
Innervates Deltoid and Teres minor

Question 14

Radial nerve

Answer 14

Formed from posterior cord
C5-T1 ventral rami contributions
Passes posterior to humerus, travels with profunda brachii (deep artery of arm) artery in the radial groove, pair seen in triangular interval
Gives off cutaneous branches (inferior lateral cutaneous nerve of arm and posterior cutaneous nerve of forearm)
Major Nerve of the posterior arm and forearm
Patient with mid-shaft humeral break - this can be damaged

Question 15

Upper plexus nerves

Answer 15

Dorsal Scapular nerve (C5) - rhomboids and lavator scapulae
Long thoracic nerve (C5-C7) - serratus anterior - can be damaged from mastectomy
Suprascapular nerve (C5-C6) - supraspinatus and infraspinatus

Question 16

Dorsal Scpular nerve (C5)

Answer 16

Passes posteriorly to reach and travel along the medial border of the scapula

Question 17

Long thoracic nerve (C5-c7)

Answer 17

Passes vertically down the neck, through the axillary inlet, and down the medial wall of the axilla.
Runs with lateral thoracic artery
lies on the superficial aspect of the serratus anterior muscle
tight against thoracic wall
Lateral thoracic artery

Question 18

Suprascapular nerve (C5-C6)

Answer 18

Passes laterally through the posterior triangle of the neck and through the suprascapular notch to enter the posterior scapular region
Nerve goes under the superior transverse scapular posterior ligament

Question 19

Nerve to the subcalvius (C5-C6)

Answer 19

Passes anterioinferiorly over the subclavian artery and vein

Question 20

Lateral pectoral nerve (C5-C7)

Answer 20

Branches from lateral cord

Question 21

Medial pectoral nerve (C8-T1)

Answer 21

Branches from medial cord
pierces pec minor to innervate pec major m.

Question 22

Upper subscapular nerve (C5-C6)

Answer 22

First branch off posterior cord
Passes posteriorly to directly innervate subscapularis muscle

Question 23

Thoracodorsal nerve (C6-C8)
“Middle subscapular nerve”

Answer 23

Second branch off posterior cord
Runs inferolaterally along posterior axiallary wall; close to thoracodorsal artery
- artery from the third portion of artery

Question 24

Lower subscapular nerve (C5-C6)

Answer 24

third branch off posterior cord
Runs inferolaterally, deep to subscrapular artery
Innervates teres major and subscapularis muscle

Question 25

Additional nerves

Answer 25

Medial brachial cutaneous nerve (C8-T1) Medial antibrachial cutanous nerve (C8-T1)

Question 26

medial Brachial cutaneous nerve (C8-T1)

Answer 26

Sensory to medial arm Second branch off medial cord Runs along medial side of axillary and branchial vv.

Question 27

Medial antebrachial cutaneous nerve (C8-T1) Not the ulnar nerve in dissection

Answer 27

Sensory to medial forearm Third branch off medial cord Initially runs with ulnar nerve but pierces deep fascia with basilic vein and enters subcutaneous tissue

Question 28

Thoracic outlet syndrome

Answer 28

Compression of subclavian artery and vein or brachial plexus Most commonly affect the nerves Causes: physical trauma, anatomical defects, tumor, poor posture, pregnancy, repetitive arm movements. More common in women Impacts to blood vessels and nerve

Question 29

Brachial plexus injuries

Answer 29

Upper plexus (C5-C6) Lower plexus (C8-T1)

Question 30

Upper plexus injury

Answer 30

C5-C6 usually results from excessive increase in angle between neck and shoulder Effects in shoulder region

Question 31

Lower plexus injury

Answer 31

C8-T1 May occur when upper limb is suddenly pulled superiorly More effects in the hand

Question 32

Muscles of the Arm - Two compartments

Answer 32

Anterior - Flexors Posterior - extensors

Question 33

Anterior flexor muscles of arm

Answer 33

Biceps brachii muscle long head Coracobrachialis muscle Biceps brachii muscle short head Brachialis muscle

Question 34

Posterior extensor muscles of arm

Answer 34

Triceps brachii muscle medial head Triceps brachii muscle lateral head Triceps brachii muscle long head Little body is conius

Question 35

Biceps brachii muscle

Answer 35

O: Know origin for each Short head: coracoid process of scapula Long head: supraglenoid tubercle of scapula (thru joint capsule) I: radial tuberosity and fascia of forearm via bicipital aponeurosis Inn: Musculocutaneous nerve Actions: supinates flexed forearm, flexes forearm (when supine) and short head resists dislocation

Question 36

Brachialis muscle

Answer 36

O: Distal half of anterior humerus I: Coronoid process and ulnar tuberosity Inn: musculocutaneous and radial nerve Actions: flexes forearm in all positions Can flex in a supine and pronated position

Question 37

Coracobrachilais muscle

Answer 37

O: Coracoid process of scapula I: middle third of medial surface of humerus Inn: Musculocutaneous nerve Actions: flexes, ADducts arm, and resists dislocation

Question 38

Triceps brachii muscle

Answer 38

O: know origin for each Long head: infraglenoid tubercle of scapula - attach to scapula Lateral Head: posterior surface of humerus superior to radial groove - attach to bone Medial head: posterior surface of humerus inferior to radial grove I: Olecranon process of the ulna and fascia of the forearm Inn: Radial nerve Actions: Chief extensor of forearm; long head resists dislocation Little extension of shoulder

Question 39

Anconeus muscle

Answer 39

triceps little helper Don't need to know o or i O: lateral epicondyle of humerus I: Olecranon process and proximal posterior ulna Inn: radial nerve Actions: assists triceps in forearm extension, stabilizes elbow joint, may abduct ulna during pronation

Question 40

Myotome and tendon testing

Answer 40

C5 - shoulder ABduction C6 - elbow flexion - C7 - elbow extension

Question 41

Reflex testing

Answer 41

C6 - biceps tendon C7 - triceps tendon

Question 42

Arteries of the arm

Answer 42

Axillary artery becomes the brachial artery at inferior border of teres major muscle runs down medial side of the arm Cross cubital fossa Medial to the tendon of the biceps brachii Branches into the radial and ulnar artery