The brachial plexus

Question 1

Describe in simple terms an overview of the brachial plexus;

Answer 1

Roots
Trunks
Divisions
Cords
Terminal/Peripheral branches of the free limb

Question 2

What are the roots of the brachial plexus?

Answer 2

C5 (With contribution from C4)
C6
C7
C8
T1 (With contribution from T2)

Question 3

What are the Trunks of the brachial plexus?

Answer 3

Superior trunk
Middle trunk
Inferior trunk

Question 4

What are the cords of the brachial plexus?

Answer 4

Lateral cord
Posterior cord
Medial cord

Question 5

What are the terminal/peripheral branches of the brachial plexus?

Answer 5

Musculocutaneous
Axillary
Median
Radial
Ulnar

Question 6

Describe nerves that branch off the roots of the brachial plexus;

Answer 6

Dorsal scapular and phrenic nerve branch off C5.

Long thoracic is formed by C5,C6,C7 contributions.

Question 7

Describe nerves that branch off the trunks of the brachial plexus;

Answer 7

The subclavian branches off the Superior Trunk.

Question 8

Describe nerves that branch off the divisions of the brachial plexus;

Answer 8

Suprascapular nerve

Question 9

Describe the nerves that branch off the cords of the brachial plexus;

Answer 9

The lateral and medial pectoral nerve branches off the later and medial cord respectively.

Upper subscapular n. , Thoracodorsal n. , lower subscapular n. , branch off the posterior cord.

Medial cutaneous nerve of forearm, medial cutaneous nerve of arm branch off the medial cord.

Question 10

Describe the anatomical route of the radial nerve;

Answer 10

The radial nerve tracks down the posterior aspect of the humerus following the radial groove then wraps around to the lateral side under biceps brachii, adjacent to brachialis.

It passes through the cubital fossa under brachioradialis passing through the heads of the supinator and shortly after it branches into the superficial (Cutaneous only) and deep branch.

The deep branch transitions into the posterior interosseous nerve where it innervates all of the extensor forearm compartment.

The superficial branch follows the posterior aspect of the radius and innervates the thumb, 2.5 digits (not tips) and thenar eminence.

Question 11

Describe the route of the median nerve;

Answer 11

Passes under the coracobrachialis transcending the medial aspect of the humerus before passing over the medial epicondyle to the anterior aspect of the cubital fossa.

The median nerve then dives under pronator teres and flexor carpi radialis.

Passing through the flexor retinaculum and innervating the thumb and 2.5 digits.

Question 12

Describe the route of the ulnar nerve;

Answer 12

The ulnar nerve passes under the head of pec minor before transcending the medial aspect of the humerus and diving posteriorly behind the distal end of the humerus in the ulnar groove.

The ulnar nerve then passes onto the medial aspect of the ulnar giving rise to the palmar cutaneous branch and dorsal cutaneous branch before passing anteriorly over the flexor retinaaculum.

The dorsal cutaneous branch goes on to give rise to the superficial branch ulnar n. (Cutaneous) and deep branch ulnar n. (most intrinsic hand mucles). Including Proper palmer digital nerves.

Question 13

What compartments does the musculocutaneous nerve innervate?

Muscle wise

Answer 13

The anterior compartment of the arm. Gives rise to lateral cutaneous nerve of the forearm too. Innervating the lateral aspect of the forearm skin.

Question 14

What compartments does the median nerve innervate? (Muscle wise)

Answer 14

3/4 Ant. aspect of forearm

1/4 of hand muscles. (3.5 digits cutaneous)

Question 15

What compartments does the ulnar nerve innervate?

Muscle wise

Answer 15

1/4 forearm muscles

3/4 of hand intrinsic muscles

Question 16

What compartments does the radial nerve innervate?

Muscle wise

Answer 16

Post compartment of arm and forearm.

Question 17

Draw/ describe the muscles involved in creating the spaces for nerves and blood vessels to pass through to the posterior compartment;

Answer 17

Teres Major, Teres Minor and triceps brachii long head insert/originate from their various structures to create the;

Triangular space; Between teres maj. and minor
Quadrangular space; (B/w TM,Tm,Tr and humerus)
Triangular interval; B/w TrLH, TM and Humerus

Question 18

What vessels/nerves use the triangular space?

Answer 18

Circumflex scapular art.

Question 19

What vessels/nerves use the quadrangular space?

Answer 19

Axillary n.

Post. circumflex humeral art. and vein

Question 20

What vessels/nerves use the triangular interval?

Answer 20

Profunda brachii art.

Radial nerve in radial/spiral groove.