Mod 2: Lecture 2 - Axilla and Brachial Plexus

Question 1

Boundaries of Axilla

Answer 1

• Anterior: pectoralis major and minor
• Posterior: scapula, latissimus dorsi, teres major
• Medial: ribs 1-4 and intercostal spaces
• Lateral: intertubercular groove of the humerus
• Base: skin and fascia of arm
• Apex: convergence of clavicle, scapula, and rib 1

Question 2

Contents of Axilla

Answer 2

1. Axillary Artery
2. Axillary Vein
3. Lymphatics
4. Brachial Plexus

Question 3

Where does the axillary artery come from?

Answer 3

• Aorta –> Brachial Trunk (BT)/ Brachiocephalic Artery –> Right Subclavian Artery + Right Common Carotid
• —- Right Subclavian –> Right Axillary artery
• Aorta —> Left Subclavian + Left Common Carotid
• — Left Subclavian –> Left Axillary Artery
• once the subclavian artery gets to the axilla, it changes names to the axillary artery

Question 4

Axillary Artery Location

Answer 4

• continuous with the subclavian artery
• — same vessel, gets a new name
• begins at the lateral border of the 1st rib and ends at the inferior border of the teres major
• — at the inferior border of the teres major, the axillary artery is continuous with the brachial artery (same vessel, new name)

Question 5

Part 1 of the axillary artery

Answer 5

• parts are named in relation to the pectoralis minor muscle
• located between the lateral border of the 1st rib and the medial border of the pectoralis minor
• Branches - Axillary I: superior thoracic artery

Question 6

Part 2 of the Axillary Artery

Answer 6

• lies posterior to pectoralis minor
• — deep to the muscle, underneath it
• Branches - Axillary II:
• — thoracoacromial trunk
• — lateral thoracic arteries

Question 7

Part 3 of the Axillary Artery

Answer 7

• Part 3: extends from the lateral border of the pectoralis minor to the inferior border of the teres major
• — emerges from underneath the pectoralis minor and goes to the lower limit of the axilla
• Branches - Axillary III:
• — subscapular artery
• — anterior humeral circumflex
• — posterior humeral circumflex

Question 8

Axillary Vein

Answer 8

• named from distal to proximal
• — following the flow of blood back to the heart
• — direction and naming is the opposite for veins and arteries
• formed at the inferior border of the teres major muscle
• — by the union of the brachial veins and the basilic vein
• ends when it joins the subclavian vein

Question 9

Lymph Nodes

Answer 9

• part of the immune system
• —body sends lymphatic fluid to the lymph nodes to decide if we need to develop to the pathogen
• 5 main groups of axillary lymph nodes
• — pectoral
• — subscapular
• — humeral
• — central
• — apical

Question 10

Pectoral Lymph Nodes

Answer 10

• anterior
• mainly receive lymph from the anterior thoracic wall
• including most of the breast

Question 11

Subscapular Lymph Nodes

Answer 11

• posterior

- receive lymph from the posterior aspect of the thoracic wall and scapular region

Question 12

Humeral Lymph Nodes

Answer 12

• receive nearly all the lymph from the upper limb

Question 13

Central Group of Lymph Nodes

Answer 13

• located along the 2nd part of the axillary artery

- receives lymph from the pectoral, subscapular, and humeral nodes

Question 14

Apical Lymph Nodes

Answer 14

• vessels from the central nodes pass to the apical nodes
• located along the fist part of the axillary artery
• drain into the supraclavicular nodes
• — surpraclavicular nodes –> subclavian lymphatic trunk –> venous system

Question 15

Spinal Nerve Plexuses

Answer 15

• Cervical: C1 - C4
• Brachial: C5 - T1
• — in the axilla
• Lumbar: L1 - L4
• Sacral: L4 - S4

Question 16

Brachial Plexus

Answer 16

• Formed by the ventral rami of spinal nerves C5, C6, C7, C8, and T1
• — those nerves are made of posterior roots (sensory) and anterior roots (motor)
• — so the brachial plexus is mixed (both motor and sensory)
• —- the rami all twist together to form one brachial plexus
• Brachial Plexus breaks up into a bunch of nerves that travel throughout the arm
• — innervation of entire upper extremity is derived from brachial plexus
• — individual arm nerves are carrying fibers from several spinal cord levels because the brachial plexus is formed from many rami

Question 17

Brachial Plexus: Branching Pattern

Answer 17

• Roots –> Trunks –> Divisions –> Cords –> Branches (Terminal)
• “Randy Travis Drinks Cold Beer”

Question 18

Brachial Plexus: Branching Pattern

1. Roots
2. Trunks

Answer 18

1. • from spinal nerves
     - — are the ventral rami
     - — so we start with 5 roots bc we have 5 ventral rami
2. (+) = add nerves together
   - combination of roots
   - 3 trunks
   - — superior (C5 + C6)
   - — middle (C7)
   - — inferior (C8 + T1)

Question 19

Brachial Plexus: Branching Pattern

3. Divisions
4. Cords

Answer 19

3. (-) = divide nerves apart
   - each trunk divides into anterior and posterior divisions
   - so there are 6 divisions
   - — 3 trunks, each splits in 2
4. (+) = add nerves together
   - formed by combinations of divisions
   - 3 cords form from 6 divisions
   - Medial, Lateral, Posterior
   - — terms refer to the nerves position relative the axillary artery
   - —- Posterior: from the posterior divisions of the three trunks
   - — Lateral: from the anterior divisions of the superior and middle trunks
   - — Medial: from the anterior division of the inferior trunk

Question 20

Brachial Plexus: Branching Pattern

5. Terminal Branches

Answer 20

5. (-) = divide nerves apart
   - two nerves from each cord, but two combine
   - —- 5 nerves total
   - Lateral Cord —> Musculocutaneous nerve + 1/2 of the Median Nerve
   - Posterior Cord —> Axillary Nerve and Radial Nerve
   - Medial Cord —> 1/2 of the Median Nerve + Ulnar Nerve

Question 21

Brachial Plexus in Relation to the Clavicle

Answer 21

• Part is above the clavicle
• — in the neck region
• — supraclavicular part of the brachial plexus
• Runs under the clavicle
• Part is below the clavicle
• — in the armpit
• — infraclavicular part

Question 22

Supraclavicular Branches of the Brachial Plexus

Answer 22

• additional branches
• — come off of roots or trunks
• Dorsal Scapular Nerve (C5)
• Long Thoracic Nerve (C5-C7)
• — goes down throughout the chest
• Suprascapular Nerve (C5-6)
• Nerve to the Subclavius (C5-6)

Question 23

Infraclavicular Branches of the Brachial Plexus

Answer 23

• additional branches
• — come off of cords
• Lateral Cord –> lateral pectoral Nerve
• Medial Cord –> medial pectoral, medial brachial cutaneous, medial antebrachial cutaneous
• — the cutaneous nerves are the only sensory nerves in the brachial plexus
• Posterior Cord –> upper subscapular, lower subscapular, thoracodorsal

Question 24

Nerves and Corresponding Muscles: Supraclavicular

1. Long Thoracic Nerve
2. Dorsal Scapular Nerve
3. Suprascapular Nerve
4. Nerve to the Subclavius

Answer 24

1. serratus anterior muscle
2. rhomboid major, rhomboid minor, levator scapularis
3. supraspinatus, infraspinatus
4. subclavius

Question 25

Terminal Branches and Corresponding Muscles

1. Axillary
2. Musculocutaneous

Answer 25

1. deltoid and teres minor

2. biceps brachii, brachialis, coracobrachialis

Question 26

Median Nerve and Branches with Corresponding Muscles: Forearm

Answer 26

• 6 1/2 muscles
• – Pronator Teres
• – Flexor Carpi Radialis
• – Palmaris Longus
• – Flexor Digitorum Superficialis
• – Flexor Digitorum Profundus (1/2)
• – Flexor Pollicis Longus
• – Pronator Quadratus

Question 27

Nerves and Corresponding Muscles: Infraclavicular

1. Lateral Pectoral
2. Medial Pectoral
3. Upper Subscapular
4. Lower Subscapular
5. Thoracodorsal

Answer 27

1. pectoralis major
2. pectoralis major and minor
3. subscapularis
4. subscapularis and teres major
5. latissimus dorsi
   - NB: the medial brachial cutaneous and medial antebrachial cutaneous nerves are sensory only - no muscle innervation

Question 28

Median Nerve and Branches with Corresponding Muscles: Hand

Answer 28

• intrinsic muscles
• Lumbricals 1 and 2
• Muscles of the Thenar Group

Question 29

Ulnar Nerve and Corresponding Muscles

Answer 29

• Forearm (1 1/2 Muscles)
• — Flexor Carpi Ulnaris
• — Flexor Digitorum Profundus (1/2)
• Hand: all remaining intrinsic hand muscles
• — those not supplied by the median nerve

Question 30

Radial Nerve and Branches with Corresponding Muscles

Answer 30

• all posterior compartment muscles of the arm and forearm

- no muscles in the hand