Axilla, Brachial Plexus and Arm Flashcards
Clinical Importance of Fascia of the Axilla and Arm
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)
Superficial veins of upper limb
Cephalic (travels laterally)
Basilic (travels medially
Both drain into axillary v
Both connected by median cubital v
Contents of the axilla
Brachial plexus of nn.
Axillary lymph nodes
Axillary v.
Axillary a.
Lymphatics of the axilla
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
Arteries of the upper limb
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
Axillary artery branches
- Superior thoracic a. (1st)
- Thoraco-acromial trunk (2nd)
a. acrominal branch
b. clavicular branch
c. deltoid branch
d. pectoral branch - Lateral throacic a. (2nd)
- Subscapular a. (3rd)
a. thoracodorsal a.
b. circumflex scapular artery - Anterior humeral circumflex a.(3rd)
- Posterior circumflex a. (3rd)
Brachial plexus divisions
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
Musculocutaneous nerve
-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
Ulnar nerves
-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
Median Nerve
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
Axillary Nerve
-Formed from posterior cord
-C5-C6 ventral rami contributions
-Circles behind humerus in quadrangular space (with post. circumflex humeral a.)
Radial nerve
-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
Dorsal scapular n.
C5
-Passes poseriorly to reach the travel along the medial border of the scapula
Long thoracic
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
Suprascapular n
C5-C6
-Passes laterally through the posterior triangle of the neck & through the suprascapular notch/foreamen to enter the posterior scapular region
N. to subclavius
C5-C6
-Passes anterioinferiorly over the subclavian artery and vein
Lateral pectoral n
C5-C7
-Branches from lateral cord
Medial pectoral n
C8-T1
-Branches from medial cord
Thoracodorsal n
C6-C8
-Second branch off posterior cord
-Runs inferolaterally along posterior axillary wall; close to thoracodorsal artery
Lower subscapular n
C5-C6
Third branch off posterior cord
-Runs inferolaterally, deep to subscapular a.
-innervates teres major and subscapular mm.
Upper subscapular n
C5-C6
First branch off posterior cord
-Passes posteriorly to directly innervate subscapularis
Thoracic Outlet Syndrome
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
Brachial Plexus (C5-C6) injuries
Usually result from excessive increase in angle between neck and shoulder
Lower Plexus (C8-T1) injuries
May occur when upper limb is suddenly pulled superiorly
Anterior flexors
Biceps brachii (long and short head)
Coracobrachiallis
Brachialis
Posterior Extensors
Triceps brachii (long, medial, and lateral head)
Biceps Brachii Muscle
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
Brachialis Muscle
O: distal half of anterior humerus
I: Coronoid process & ulnar tuberosity
Inn: musculocutaneous and radial n.
Action(s): flexes forearm in all positions
Coracobrachialis Muscle
O: Coracoid process of scapula
I: middle third of medial surface of humerus
Inn: musculocutaneous n.
Action(s): flexes, adducts arm, and resists dislocation
Triceps Brachii Muscle
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
Anconeus muscle
Inn: radial n.
Action: assists triceps in forearm extension, stabilizes elbow joint, may abduct ulna during pronation
Myotome and tendon testing (C5-C7)
C5: shoulder abduction
C6: elbow flexion
C7: elbow extension
Medial brachial cutaneous n
C8-T1
-Sensory to medial arm
-Second branch off medial cord
-Runs along medial side of axillary & brachial vv.
Medial antebrachial cutaneous n.
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
Arteries of the arm
-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.
Brachial artery braches
- Profunda brachii a. (deep brachial a. or deep artery of the arm)- radial collateral and middle collateral
- Humeral nutrient a.
- Superior ulnar collateral s.
- Inferior ulnar collateral a.
- Radial artery
- Ulnar a.
