L34 Axilla, Brachial Plexus

Question 1

What are the boundaries of the axilla?

Answer 1

Anterior wall: Anterior axillary fold:
Pectoralis major
& minor (fascia)

Posterior wall: Posterior axillary fold:
Scapula,
subscapularis,
teres major,
latissimus dorsi

**Medial wall**:
 Serratus anterior (& thoracic wall)

Lateral wall: Proximal humerus

Reference lines:
Anterior axillary line
Midaxillary line
Posterior axillary line

Question 2

What is contained in the Axilla?

Answer 2

Axillary artery (& brs.)
 Axillary vein (& tribs.)
 Axillary lymph nodes (& assoc. lymphatic vessels)
 Brachial plexus (cords & branches)
 Embedded in (and protected by) axillary fat

Apex: Cervico-axillary canal (open
to root of neck)

Question 3

What are the borders of the axillary a?

Where are the compression points?

Answer 3

1. Begins:
   Lateral border: 1st rib
   (continuation: subclavian a)
2. Divided into 3 parts:
   Pectoralis minor

1^st part: Proximal to PMi
2^nd part: Deep to PMi
3^rd part: Distal to PMi

3. Ends:
   Inferior border: Teres major
   (posterior axillary fold)
   (becomes: brachial a)

Compression (for bleeding):
At 1st and 3rd parts

Question 4

What arteries anastomose at the surgical neck of the humerus?

What are their origins?

Answer 4

1. Anterior circumflex humeral a
2. Posterior circumflex humeral a

Both come off 3rd pard of axillary a

Question 5

What arteries anastomose around the scapula and why is this important?

Answer 5

Suprascapular a goes “over” superior transverse scapular ligament then travels along the lateral border of the scapula to the inferior angle of the scapula
Dorsal scapular a travels along the medial border of the scapula and anastomoses with the suprascapular a at the inferior angle of the scapula.
These two have anastomosing branches around the scapula

The circumflex scapular a comes off the 3rd part of the axillary artery and anstomoses w/ branches from the suprascapular a and dorsal scapular a.

This allows blood to bypass a restriction in the subclavian or axillary arteries

Most effective if the restriction is proximal to origin of the subscapular a (1st branch of 3rd part of axillary a)

Question 6

Describe the axillary v and its tributaries

Answer 6

Brachial v (deep) and basilic v (medial) join at the inferior border of teres major to form the axillary v. The cephalic v (lateral) drains to the axillary v before the axillary v becomes the subclavian v.

Question 7

What are the 5 major parts of the brachial plexus and what are the composed of?

Answer 7

1. Roots:
   anterior primary rami of C5-T1 spinal nerves
2. Trunks:
   Superior (C5+6)
   Middle (C7)
   Inferior (C8+T1)
3. Divisions:
   Each trunk has an anterior and posterior division
4. Cords:
   Lateral: Anterior Divisions of superior & middle trunks
   Posterior: Posterior divisions from superior, middle and inferior trunks
   Medial: Anterior division of inferior trunk
5. Branches (nerves)
   Musculocutaneous: from lateral cord
   Median: from lateral and medial roots of lateral and medial cords
   Axillary & Radial: branches of posterior cord
   Ulnar: from medial cord

Question 8

What composes the supraclavicular (neck) portion of the brachial plexus?

What nerves originate in this area?

Answer 8

The neck portion is composed of the 1st and 2nd and second parts of the brachial plexus; roots and trunks.

Nerves that originate from roots:
The dorsal scapular n (C5) and long thoracic n (C5-7)

Nerves that originate from trunks:
The suprascapular n and subclavian n (C5,6)

Question 9

What muscles to anterior divisions innervate?

and posterior divisions?

Answer 9

Anterior divisions: inn. flexor mm.

Posterior divisions: inn. extensor mm.

Question 10

What are the terminal branches of the Lateral Cord?

Side branches?

Answer 10

Terminal:

1. Musculocutaneous n
2. Lateral root of median n

Side branch:
1. Lateral pectoral n

Question 11

What are the terminal branches of the Medial cord?

Side branches?

Answer 11

Terminal:

1. Ulnar n
2. Medial root of median n

Side branches:

1. Medial pectoral n
2. Medial Cutaneous nerve of the arm
3. Medial cutaneous nerve of the forearm

Question 12

What are the Terminal and side branches of the Posterior Branch?

Answer 12

Terminal:

1. Axillary n
2. Radial n

Side branches:

1. Upper subscapular n
2. Thoracodorsal n
3. Lower subscapular n

Question 13

Answer 13

1. Dorsal scapular n
2. Long thoracic n
3. Suprascapular n
4. Subclavian n
5. Lateral pectoral n
6. Lateral root of median n
7. Musculocutaneous n
8. Medial pectoral n
9. Medial cutaneous n of arm
10. Medial cutaneous n of forearm
11. Medial root of median n
12. Ulnar nerve
13. Median n (flexors)
14. Upper subscapular n
15. Thoracodorsal n
16. Lower subscapular n
17. Radial n
18. Axillary n

Question 14

Traveling Companions:

1. Suprascapular notch
2. Surgical neck: humerus
3. Medial border of scapula
4. Lateral thoracic wall: Midaxillary line
5. Lateral thoracic wall: Posterior axillary line
6. Deltopectoral groove
7. Deltopectoral triangle
8. Pectoralis minor
9. Axillary artery

Answer 14

1. Suprascapular notch:
   Suprascapular artery/v
   Suprascapular nerve
   (“Army over Navy”
2. Surgical neck: humerus:
   Posterior circumflex humeral a/v
   Axillary nerve
3. Medial border of scapula:
   Transverse cervical a/v and spinal accessory nerve: Trapezius
   Dorsal scapular a/v and dorsal scapular nerve: Rhomboids, levator scapulae
4. Lateral thoracic wall: Midaxillary line:
   Lateral thoracic artery (and vein)
   Long thoracic nerve: Serratus anterior
5. Lateral thoracic wall: Posterior axillary
   line:
   Thoracodorsal artery (and vein)
   Thoracodorsal nerve: Latissimus dorsi
6. Deltopectoral groove:
   Cephalic vein
7. Deltopectoral triangle:
   Cephalic vein
   Thoracoacromial artery
   Lateral pectoral nerve
8. Pectoralis minor:
   Pierced by medial pectoral nerve
   Reference muscle for 3 divisions of axillary artery
9. Axillary artery:
   Cords of brachial plexus named by position relative to axillary artery