Lecture 5.2

Question 1

Sometimes the brachial plexus can bud out from C4,5,6,7,8 and sometimes from C6,7,8,T1,2. What is the name of these anomalies?

Answer 1

Pre-fixed brachial plexus

Post-fixed brachial plexus

Question 2

Why is the upper limb innervated by the ventral rami of the spinal nerves?

Answer 2

Upper limb buds out from the anterior body wall and takes with it the ventral nerve supply which is why the ventral rami supply the upper limb.

Question 3

What is the brachial plexus divided into along its path?

Answer 3

5 Roots -> 3 trunks -> 6 divisions -> 3 cords -> 5 terminal branches

Question 4

What are the 3 trunks of the brachial plexus?

Answer 4

Superior (C5 - C6)

Middle (C7)

Inferior (C8 - T1)

Question 5

What do the 3 trunks divide into?

Answer 5

Each trunk has an anterior and posterior division

Question 6

What do anterior and posterior division fibers innervate?

Answer 6

Anterior division fibers supply flexor muscles and skin overlying them.

Posterior division fibers supply extensor muscles and skin overlying them.

Question 7

What structure do the 3 cords of the brachial plexus surround?

Answer 7

The axillary artery

Question 8

What divisions form the lateral cord of the brachial plexus?

Answer 8

Anterior divisions of the superior trunk and the middle trunk.

Question 9

What divisions form the medial cord?

Answer 9

Anterior division of inferior trunk continues as the medial cord

Question 10

What divisions do the anterior and lateral cords contain as a whole?

Answer 10

Lateral and medial cord contain all anterior divisions.

Question 11

What divisions form the posterior cord?

Answer 11

All 3 posterior divisions form the posterior cord.

Question 12

What structures form the M shape of the brachial plexus?

Answer 12

M shape formed by the terminal branches of the lateral and medial cord

Question 13

Where are the cords formed relative to the clavicle?

Answer 13

inferior to the clavicle the cords are formed

Question 14

What nerve arises from the upper limb of the ‘M’? What cord can this nerve be traced back to?

Answer 14

upper limb of the m pierces coracobrachialis this is the musculocutaneous nerve. This can be traced back to the lateral cord

Question 15

What is the terminal branch formed by the middle limb of the ‘M’?

Answer 15

Middle limb of the m is the median nerve. It has a root from the lateral cord and the medial cord.

Question 16

What is the terminal branch formed by the lower limb of the ‘M’?

Answer 16

Lower limb of the m is the ulnar nerve.

Question 17

Which nerve pierces coracobrachialis?

Answer 17

The musculocutaneous nerve

Question 18

What 2 muscles does the musculocutaneous nerve run through?

Answer 18

Deep to the Biceps and superficial to the brachialis

Question 19

What happens to the musculocutaneous nerve after it runs out of motor branches?

Answer 19

Musculocutaneous nerve continues after the elbow and becomes the lateral cutaneous nerve of the forearm supplying the skin of the lateral side of the forearm.

Question 20

What roots does the ulnar nerve get?

Answer 20

Ulnar nerve is a branch of the medial cord of the brachial plexus which was formed by the anterior division of the lower trunk. Most people get some contribution from C7. But is mainly innervated by C8 and T1.

Question 21

Where does the ulnar nerve run in the arm?

Answer 21

ulnar nerve runs down medial side of the brachial artery and then moves under the medial epicondyle. It is vulnerable to trauma at that location.

Question 22

Where does the ulnar nerve run in the forearm?

Answer 22

In forearm ulnar nerve is found under the Flexor carpi ulnaris and then runs superficially to the flexor retinaculum into the palm of the hand.

Question 23

What does the ulnar nerve supply?

Answer 23

ulnar nerve primarily supplies the hand with the exception of the lateral 2 lumbricals, the opponens pollicis, the abductor pollicis brevis, and the flexor pollicis brevis. (1 ‘+ 2’ LOAF which is a mnemonic for the thenar eminence muscles which are innervated by the median nerve)

Question 24

What muscles of the forearm does the median nerve supply?

Answer 24

Median nerve supplies the anterior compartment of the forearm. exception is FCU and the medial 2 heads of FDP.

Question 25

What muscles in the palm of the hand does the ulnar nerve innervate?

Answer 25

Everything in the palm of the hand except what the median nerve does. (1’+2’ LOAF)

Question 26

What is the cutaneous distribution of the ulnar nerve?

Answer 26

ulnar nerve does medial 1 and a half fingers anteriorly and posteriorly.and the palm underneath

Question 27

What nerve roots, divisions, and cords does the median nerve arise from?

Answer 27

Median nerve comes from median and lateral cords and is formed by all the anterior divisions. from ventral rami of C5,6,7,8,T1.

Question 28

How does the median nerve travel along the arm?

Answer 28

Median nerve is found either lateral to or anterior to the brachial artery. This nerve crosses the brachial artery medially into the cubital fossa.

Question 29

What are the contents of the cubital fossa from laterally to medially?

Answer 29

Radial Nerve then Tendon of biceps then brachial artery then the median nerve. (RBAN from laterally to medially)

Question 30

What is the cutaneous distribution of the median nerve?

Answer 30

Anteriorly all the palm and 3 and a half fingers from lateral hand to medial.
Posteriorly the tips of the fingers of the area the median nerve innervates anteriorly.

Question 31

How does the median nerve travel through the forearm?

Answer 31

Median nerve enters anterior compartment of the forearm underneath the arch of FDS. Fibrous Arch of FDS created by origin at the radius and the medial epicondyle. Median nerve runs superficially to FDP and deep to FDS’ fibrous arch

Question 32

What nerves supply the lumbricals?

Answer 32

medial 2 lumbricals supplied by the ulnar nerve and lateral 2 lumbricals by the median nerve.

Question 33

Why is there no tingling or numbness during carpal tunnel syndrome?

Answer 33

Palmar cutaneous nerve goes over the flexor retinaculum to supply the cutaneous nerve supply and so it isn’t entrapped with the rest of the median nerve.

Question 34

Where in the brachial plexus do the radial and axillary nerves arise from?

Answer 34

Posterior cord contains all posterior divisions and creates the radial and axillary nerves.

Question 35

What spaces do the axillary nerve and radial nerve go into the posterior compartment and where is this relative to teres major?

Answer 35

Axillary nerve goes above teres major and below teres minor (quadrangular space) and radial nerve below teres major (triangular interval).

Question 36

What spinal roots does the axillary nerve receive its innervation from?

Answer 36

C5, C6

Question 37

Why is shoulder dislocation a problem for the axillary nerve?

Answer 37

The anterior branch of the axillary nerve goes through quadrangular space and then winds around the humeral surgical neck along with posterior humeral circumflex artery. Shoulder dislocation can damage this branch.

Question 38

What muscles does axillary nerve supply?

Answer 38

Teres minor
Deltoids
Long head of the triceps (not mentioned in lectures but found in many sources I read)

Question 39

What branches of the axillary nerve supply the deltoids?

Answer 39

anterior and posterior branches of axillary nerve supply deltoids

Question 40

What structures does the radial nerve supply?

Answer 40

Radial nerve supplies triceps and posterior compartment of the forearm.

Question 41

What is the pathway the radial nerve takes in the arm?

Answer 41

emerges beneath teres major and spirals around the back of the humerus and follows profunda brachii artery. Radial nerve branches off really early and at the spiral groove it sends off branches to the posterior compartment of the forearm.

Question 42

What muscle does the radial nerve go under in the forearm?

Answer 42

Brachioradialis

Question 43

What structures pass under brachioradialis?

Answer 43

The radial nerve and artery

Question 44

What branch does the radial nerve give off before heading under brachioradialis?

Answer 44

before the radial nerve splits under the cover of brachioradialis it gives off all of its motor fibers via the posterior interosseus nerve which runs deeply and supplies all the extensor compartment of the forearm’s muscles

Question 45

What is the cutaneous distribution of the radial nerve in the hand?

Answer 45

the dorsum of the hand with the exception of the nailbeds.

Question 46

What cutaneous nerves supply the lateral side of the arm and forearm?

Answer 46

“ARM”
Axillary nerve over the deltoids.
Radial nerve on the lateral side of the arm.
Musculocutaneous nerve on the lateral side of the forearm gives off a branch called the lateral cutaneous branch of the forearm.

Question 47

What cutaneous nerves supply the medial side of the arm and forearm?

Answer 47

Skin down medial side of the arm is by medial cutaneous nerve of arm and forearm. These are direct branches of the medial cord.

Question 48

What structure are the 3 cords of the brachial plexus named after?

Answer 48

The axillary artery