Axilla, Brachial Plexus and Arm

Question 1

Clinical Importance of Fascia of the Axilla and Arm

Answer 1

Deep fascia and subcutaneous tissue is located deep to skin.
Clinical Importance: fascial compartments of the upper limb contain and direct the spread of infection or hemorrhage in the limb (Compartment syndrome)

Question 2

Superficial veins of upper limb

Answer 2

Cephalic (travels laterally)
Basilic (travels medially
Both drain into axillary v
Both connected by median cubital v

Question 3

Contents of the axilla

Answer 3

Brachial plexus of nn.
Axillary lymph nodes
Axillary v.
Axillary a.

Question 4

Lymphatics of the axilla

Answer 4

Humeral: upper limb
Pectoral: anterior thoracic walll & most of the breast
Subscapular: posterior thoracic wall & scapular region
Central: tributries from humeral, subscapular, & pectoral groups
Apical: drain all other groups of nodes

Question 5

Arteries of the upper limb

Answer 5

Subclavian a: arises from the brachiocephalic trunk of the right directly from the arch of the aorta on the left
Subclavian a. becomes axillary a. at the lateral border of 1st rib

Question 6

Axillary artery branches

Answer 6

1. Superior thoracic a. (1st)
2. Thoraco-acromial trunk (2nd)
   a. acrominal branch
   b. clavicular branch
   c. deltoid branch
   d. pectoral branch
3. Lateral throacic a. (2nd)
4. Subscapular a. (3rd)
   a. thoracodorsal a.
   b. circumflex scapular artery
5. Anterior humeral circumflex a.(3rd)
6. Posterior circumflex a. (3rd)

Question 7

Brachial plexus divisions

Answer 7

Roots (5): emerge through anterior and middle scalene
Trunks (3): lie superior to the 1st rib & course w/ subclavian a.
Divisions (6): split off behind clavicle; anterior & posterior each trunk
Cord (3): posterior to pectoralis minor m. & related to 2nd part of axillary a
Branches (5): terminal

Question 8

Musculocutaneous nerve

Answer 8

-Formed from lateral cord
-C5-C7 ventral rami contributions
-Pierces thru coracobrachialis m. : descends between biceps brachii and brachialis mm.
-Major N of the anterior arm
-Continues as lateral cutaneous nerve of arm: innervates skin of lateral forearm

Question 9

Ulnar nerves

Answer 9

-Formed from medial cord
-C8-T1 ventral rami contributions
-Located medial to brachial a. in arm
-Innervated NOTHING in arm (powerhouse of the hand)
-Runs behind medial epicondyle
-Major N of the hand

Question 10

Median Nerve

Answer 10

Formed form 1/2 lateral cord and 1/2 medial cord
-C6-T1 ventral rami contributions
-Passes medial to arm mm. : lateral to brachial a. proximally, distally crosses to medial side of brachial artery
-Innervates NOTHING in arm
-Major N in the anterior forearm

Question 11

Axillary Nerve

Answer 11

-Formed from posterior cord
-C5-C6 ventral rami contributions
-Circles behind humerus in quadrangular space (with post. circumflex humeral a.)

Question 12

Radial nerve

Answer 12

-Formed from posterior cord
-C5-T1 ventral rami contributions
-Passes posterior to humerus travels with profunda brachii a. in the radial groove, pair seen in triangular interval
-Gives off cutaneous braches: inferior lateral cutaneous n. of arm and posterior cutaneous n. of forearm
-Major N of the posterior arm and forearm

Question 13

Dorsal scapular n.

Answer 13

C5
-Passes poseriorly to reach the travel along the medial border of the scapula

Question 14

Long thoracic

Answer 14

C5-C7
-Passes vertically down the neck, through the axillary inlet, and down the medial wall of the axilla
-Runs with lateral thoracic a.
-Lies on the superficial aspect of the serratus anterior muscle

Question 15

Suprascapular n

Answer 15

C5-C6
-Passes laterally through the posterior triangle of the neck & through the suprascapular notch/foreamen to enter the posterior scapular region

Question 16

N. to subclavius

Answer 16

C5-C6
-Passes anterioinferiorly over the subclavian artery and vein

Question 17

Lateral pectoral n

Answer 17

C5-C7
-Branches from lateral cord

Question 18

Medial pectoral n

Answer 18

C8-T1
-Branches from medial cord

Question 19

Thoracodorsal n

Answer 19

C6-C8
-Second branch off posterior cord
-Runs inferolaterally along posterior axillary wall; close to thoracodorsal artery

Question 20

Lower subscapular n

Answer 20

C5-C6
Third branch off posterior cord
-Runs inferolaterally, deep to subscapular a.
-innervates teres major and subscapular mm.

Question 21

Upper subscapular n

Answer 21

C5-C6
First branch off posterior cord
-Passes posteriorly to directly innervate subscapularis

Question 22

Thoracic Outlet Syndrome

Answer 22

Compression of subclavian a. and v. or brachial plexus
-Most commonly affects the nerves
Causes: physical trauma, antatomical defects, tumor, poor posture, pregnancy, repetitive arm movements
-More common in women

Question 23

Brachial Plexus (C5-C6) injuries

Answer 23

Usually result from excessive increase in angle between neck and shoulder

Question 24

Lower Plexus (C8-T1) injuries

Answer 24

May occur when upper limb is suddenly pulled superiorly

Question 25

Anterior flexors

Answer 25

Biceps brachii (long and short head)
Coracobrachiallis
Brachialis

Question 26

Posterior Extensors

Answer 26

Triceps brachii (long, medial, and lateral head)

Question 27

Biceps Brachii Muscle

Answer 27

O: short head- coracoid process of scapula
long head- supraglenoid tubercle of scapula
I: Radial tuberosity & fascia of forearm via bicipital aponeurosis
Inn: Musculocutaneous n.
Action(s): supinate flexed forearm, flexes forearm (when supine), and short head resists dislocation

Question 28

Brachialis Muscle

Answer 28

O: distal half of anterior humerus
I: Coronoid process & ulnar tuberosity
Inn: musculocutaneous and radial n.
Action(s): flexes forearm in all positions

Question 29

Coracobrachialis Muscle

Answer 29

O: Coracoid process of scapula
I: middle third of medial surface of humerus
Inn: musculocutaneous n.
Action(s): flexes, adducts arm, and resists dislocation

Question 30

Triceps Brachii Muscle

Answer 30

O: long head- infraglenoid tubercle of scapula
lateral head- posterior surface of humerus superior to radial groove
medial head- posterior surface of humerus inferior to radial groove
I: Olecranon process of the ulna and fascia of forearm
Inn: Radial n.
Action(s): chief extensor of forearm; long head resists dislocation

Question 31

Anconeus muscle

Answer 31

Inn: radial n.
Action: assists triceps in forearm extension, stabilizes elbow joint, may abduct ulna during pronation

Question 32

Myotome and tendon testing (C5-C7)

Answer 32

C5: shoulder abduction
C6: elbow flexion
C7: elbow extension

Question 33

Medial brachial cutaneous n

Answer 33

C8-T1
-Sensory to medial arm
-Second branch off medial cord
-Runs along medial side of axillary & brachial vv.

Question 34

Medial antebrachial cutaneous n.

Answer 34

C8-T1
-Sensory to medial forearm
-Third branch off medial cord
-Initially runs with ulnar n. but pierces deep fascia with basilic v. & enters subcutaneous tissue

Question 35

Arteries of the arm

Answer 35

-Axillary a. becomes brachial a. at inferior border of teres major m.
-In proximal arm: lies on medial side
-In distal arm: moves laterally to assume position midway between the lateral epicondyle and hte medial epicondyle of the humerus
-Crosses anteriorly to the elbow joint where it lies immediately medial to the tendon of the biceps brachii m. in cubital fossa
-Branches into the radial & ulnar aa.

Question 36

Brachial artery braches

Answer 36

1. Profunda brachii a. (deep brachial a. or deep artery of the arm)- radial collateral and middle collateral
2. Humeral nutrient a.
3. Superior ulnar collateral s.
4. Inferior ulnar collateral a.
5. Radial artery
6. Ulnar a.