brachial plexus

Question 1

What forms the brachial plexus?

Answer 1

anterior rami of C5 &T1

Question 2

What are the 5 parts of brachial plexus?

Answer 2

Roots Trunks Divisions Cords Branches (Read That Damn Cadaver Book)

Question 3

What are the different roots?

Answer 3

refers to C5, C6, C7, C8 & T1

Question 4

What are the different trunks?

Answer 4

C5&C6-superior trunk
C7- middle trunk
C8 & C9 - inferior trunk
they travel laterally (crossing the posterior triangle of the neck)

Question 5

What are the different divisions?

Answer 5

Each trunk subdivides into superior and inferion divisions i.e 6 divisions formed (they’ll leave the posterior triangle and pass into the axilla then recombine)

Question 6

how and what cords are formed?

Answer 6

The 6 divisions recombine into 3 main chords:
-medial cord (1) : anterior division of inferior trunk
-lateral cord(2) : anterior division of superior trunk and anterior division of middle trunk
-posterior cord (3) : posterior divisions of inferior, superior and middle trunks

Question 7

What are the 5 main branches of the brachial plexus
?

Answer 7

1.Musculocutaneous nerve
2.Axillary nerve
3.Medial nerve
4.Radial nerve
5.Ulnar nerve

Question 8

What is the route of the musculocutaneosu nerve?

Answer 8

*notes it’s a terminal branch of the lateral cord

route : to simplify its pierces coracobrachialis - emerges between biceeps brachii & brachialis - continues in lateral aspect of forearm as the lateral cutaneous nerve

Question 9

What muscles does the musculocutaneous nerve supply?

Answer 9

mnemonic: BBC
-biceps brachii (supinates and flexes)
-brachioradialis (flexes)
-coracobrachialis (flexes)

Question 10

What skin area does the musculocutaneous nerve innervate?

Answer 10

lateral aspect of forearm

Question 11

What is the course of the axillary nerve?

Answer 11

(note it’s a continuation of the posterior cord)

course:
-exits axilla at inferior border of subscapularis muscle via quandrangular space
-passes medially to surgical neck of humerus
-divides into 3 terminal branches : posterior , anterior and articular terminal branches

from origin to inferior border of subscapularis, then to long head of triceps, surgical neck of humerus finally runs beneath the deltoid muscle

Question 12

What muscle does axillary nerve innervate?

Answer 12

deltoid and pectoralis minor

Question 13

What skin areas does the axillary nerve innervate?

Answer 13

-Glenohumeral joint
-skin of deltoid/skin over shoulder : the so called ‘‘regimental badge area’’

Question 14

What is the course of the median nerve ?

Answer 14

(arises from medial and lateral cords, hence has fibers of C6-T1 sometimes C5 too)

course:
-originates in axilla

-descends down the arm lateral to brachial a.

-half down the arm its crosses over to medial side

-enters anterior compartment of forearm via cubital fossa

-travels between flexor digitorum profondus and superficialis in forearm

-gives off 2 branches: anterior interosseus & palmar cutaneous nerve

-median nerve then enters hand via carpal tunnel

-before terminating it divides into recurrent and palmar digit branches

runs through thelateral anterior portion of the arm and medial portion of forearm before finishing its path at the hand and digits in recurrent and palmar digit branches resp.

Question 15

What muscles are innervated by the medain nerve?

Answer 15

basically most anterior forearm and some intrinsinc muscles

*Superficial & intermediate layers of 4arm: pronator teres/flexor carpi radialis/palmaris longus

*Deep flexors in 4arm(done speccifically by anterior interosseus nerve) : flexor pollicis longus/pronator quadratus/ lateral half of flexor digitorum longus

*Hand (done via recurrent and palmar digital branches respectively) :
thenar muscles & lateral 2 lumbricals

Question 16

What skins areas are innervated by the median nerve ?

Answer 16

-Skin of lateral palm (done by palmar cutaneous nerve)

-Pamar surface (done palmar digital branch)

Question 17

What is the course of the radial nerve?

Answer 17

arises from posterior cord, C5-T1

course:
-exits axilla inferiorly

-supplies branches to long & lateral heads of triceps brachii

-travels down the arm in the radial groove of the humerus

-as it descends it wraps around the humerus laterally and supplies a branch to medial head of biceps brachii

-travels anterior to teh lateral epicondyle of humerus through ‘‘cubital fossa’’

-enters forearm
-terminates by diving into 2 branches : deep branch (motor) & superficial branch (sensory)

arises in the axillary region and descends down along the posterior surface of the humerus passes through the cubital fossa and terminates in the posterior compartment of the forearm, by dividing into two terminal branches: superficial (sensory) and deep (motor).

Question 18

What muscles are supplied by radial nerve ?

Answer 18

-Muscles of posterior compartment of forearm i.e the extensors
-3 heads of triceps brachii
-Brachioradialis
-Extensor carpi radialis longus

Question 19

What skin areas are innervated by the radial nerve?

Answer 19

anterolateral arm, distal posterior arm, posterior forearm, and posterolateral wrist and hand areas

Question 20

what is the course of the ulnar nerve?

Answer 20

continuation of medial cords, contains fibers of C8-T1

course:
-rises from brachial plexus

-descends in a plane between axilary vein and artery

-proceeds down the medial aspect of arm with brachial artery found laterally

-at the midpoint of the arm the nerve penetrates the medial fascia septum

-enters the posterior compartmnent of the arm

-passes anterior to the elbow through the ulnar tunnel

-gives rises to an articular branch to supply elbow joint

-in the 4arm it pierces the 2 heads of flexor carpi ulnaris

-it travels ddeep to FCU alongisde ulna

-branches into 3: muscular branch, palmar cutaneous branch,dorsal cutaneous branch

• then it travels superficial to the flexor retinaculum

-enters the hand through Guyon’s/ Ulnar canal

-Terminates by giving rise to superficial and deep branches

travels down the inner side of the arm, passes through the cubital tunnel at the elbow, and continues into the hand through guyon’s canal

Question 21

What muscles ares upplied by the ulnar nerve ?

Answer 21

flexor muscles of 4 arm : flexor carpi ulnaris & flexor digitorum profondus (muscular branch)

Intrinsic muscles of hand: Hypothenar muscles (FDMB, ADM , ODM) / medial 2 lumbricals / adductor pollicis / palmar & dorsal interossei of hand – n.b it’s done by the deep branch
superficial branch — palmaris brevis

Question 22

Which skin areas are innervated by ulnar nerve and/or it’s branches?

Answer 22

medial half of palm (palmar cutaneous branch)

dorsal surface of medial one and half fingers & associated dorsal hand area (dorsal cutaneous branch)

Question 23

What are the signs and symptoms of injury to the axillary nerve?

Answer 23

Numbness over part of the outer shoulder.

Pain in the shoulder region.

Shoulder weakness, especially when lifting the arm up and away from the body.

Question 24

signs and symptoms of injuries to the musculocutaneous nerve

Answer 24

weakness in elbow flexion or shoulder flexion,

atrophy of the biceps brachii,

pain or paresthesia at the lateral forearm.

Question 25

signs and symptoms of injuries to the median nerve

Answer 25

Difficulty or even inability to turn the hand over or flex the wrist down.

Tingling or numbness in the forearm, thumb and the three adjacent fingers.

Weakness with gripping and inability to move the thumb across the palm.

Question 26

signs and symptoms of injuries to the radial nerve

Answer 26

Abnormal sensations in the back and thumb side of the hand, or in the thumb, 2nd, and 3rd fingers.

Weakness, loss of coordination of the fingers.

Problem straightening the arm at the elbow.

Problem bending the hand back at the wrist, or holding the hand.

Question 27

signs and symptoms of injuries to the ulnar nerve

Answer 27

Abnormal sensations in the little finger and part of the ring finger, usually on the palm side.

Weakness, loss of coordination of the fingers.

Claw-like deformity of the hand and wrist.

Pain, numbness, decreased sensation, tingling, or burning sensation in the areas controlled by the nerve.