Axilla and Brachial Plexus

Question 1

Where is the axilla?

Answer 1

Pyramidal space inferior to the shoulder joint and just superior to the armpit

Question 2

Where is the medial wall of the axilla?

Answer 2

Superolateral aspect of the chest

Question 3

Where is the axilla a gateway to?

Answer 3

The upper limb

Question 4

Where is the pectoralis major?

Answer 4

Forms anterior wall of axilla, lower border is contained in the inferior edge of the anterior axillary field

Question 5

What actions does pectoralis major perform?

Answer 5

One of main muscles of climbing (alongside latissimus dorsi), important accessory muscle of inspiration

Question 6

What is the axillary vein a continuation of?

Answer 6

Continuation of the brachial vein (deep vein of the arm)

Question 7

Where does the brachial vein become the axillary vein?

Answer 7

At lower border of teres major

Question 8

What is the association between the teres major and the axilla?

Answer 8

Contributes to posterior wall of axilla, inferior border corresponds to the inferior extent of the axilla

Question 9

Where can the pulsations of the subclavian artery be palpated?

Answer 9

Where the artery crosses the first rib

Question 10

Where does the subclavian artery become the axillary artery?

Answer 10

At the lateral border of the first rib

Question 11

Where does the brachial plexus supply and what is it formed from?

Answer 11

Supplies the upper limb; formed from a very specific intertwining of the anterior rami of spinal nerves C5-T1

Question 12

What does the brachial plexus contain (from proximal to distal)?

Answer 12

Roots, trunks, divisions, cords, named nerves

Question 13

What are the roots of the brachial plexus?

Answer 13

Anterior rami of C5-T1 spinal nerves, which mix their fibres to form trunks

Question 14

What are nerve trunks?

Answer 14

Combinations of roots which give rise to divisions

Question 15

What are the trunks of the brachial plexus?

Answer 15

Superior = combined anterior rami of C5-6 spinal nerves
Middle = anterior ramus of C7 spinal nerve
Inferior = combined anterior rami of C8 and T1 spinal nerves

Question 16

What are nerve divisions?

Answer 16

Anterior and posterior divisions of each trunk which combine to give cords

Question 17

What are the cords of the brachial plexus named according to?

Answer 17

Their relationship to the axillary artery

Question 18

What are the cords of the brachial plexus?

Answer 18

Medial = direct continuation of anterior division of inferior trunk
Lateral = formed from the anterior divisions of the superior and middle trunks
Posterior = formed from posterior divisions of all three trunks

Question 19

What are the named nerves of the brachial plexus?

Answer 19

Ulnar nerve = continues directly from medial cord
Musculocutaneous nerve = continues directly from lateral cord
Axillary and radial nerves = divisions of posterior cord
Median nerve = contributed to by the medial and lateral cords

Question 20

Where are the roots and trunks of the brachial plexus located?

Answer 20

Lie mainly between the anterior and middle scalene muscles in the root of the neck

Question 21

Where are the divisions of the brachial plexus located?

Answer 21

Lie immediately posterior to the subclavian vessels in the root (deep to the clavicle)

Question 22

Where are the cords of the brachial plexus located?

Answer 22

Lie around the axillary artery, which is distal to the first rib

Question 23

Where does the musculocutaneous nerve enter the axilla to supply?

Answer 23

The coracobrachialis muscle, also supplies other muscles of the anterior compartment of the arm (biceps brachii and brachialis)

Question 24

Where do both the axillary nerve and the radial nerve pass through the axilla to?

Answer 24

Into the posterior compartment of the arm

Question 25

Where is the axillary nerve located?

Answer 25

Lies superior to radial nerve and wraps around the posterior aspect of the surgical neck of the humerus (vulnerable to injury in shoulder dislocation or fractured humerus neck)

Question 26

Where is the radial nerve located?

Answer 26

Wraps around posterior aspect of the mid-shaft of the humerus (may be damaged by mid-shaft humeral fracture)

Question 27

Where does the ulnar nerve pass through the axilla to enter?

Answer 27

The medial compartment of the arm

Question 28

What is the most medial of the named nerves of the brachial plexus?

Answer 28

The ulnar nerve

Question 29

What does the median nerve form?

Answer 29

Middle of “M-shaped” configuration of the named nerves within the axilla