Brachial plexus

Question 1

Where does the dorsal scapular nerve originate from?

Answer 1

from the C5 root

Question 2

Where does the long thoracic nerve originate from?

Answer 2

from the C, C6, C7 root

Question 3

Where does the suprascapular nerve originate from?

Answer 3

from the upper trunk

Question 4

Where does the lateral pectoral nerve originate from?

Answer 4

from the lateral chord

Question 5

Where does the upper supscapular nerve originate from?

Answer 5

posterior chord

Question 6

Where does the lower supscapular nerve originate from?

Answer 6

posterior chord

Question 7

Where does the thoracodorsal nerve originate from?

Answer 7

posterior chord

Question 8

Where does the medial cutaneous nerve of the arm originate from?

Answer 8

medial chord

Question 9

Where does the medial cutaneous nerve of the forarm originate from?

Answer 9

medial chord

Question 10

Where does the medial pectoral nerve originate from?

Answer 10

medial chord

Question 11

What does the dorsal scapular nerve innervate?

Answer 11

rhomboid major + minor, levator scapulae

Question 12

What does the long thoracic nerve innervate?

Answer 12

supplies serratus anterior , descends posterior to roots of brachial plexux + anterior to root of scalenus posterior muscles, course along chest wall in srface of serratus anterior muscle

Question 13

What is a pathology associated with the long thoracic nerve?

Answer 13

paralysis of the serratus anterior + winged scapula

Question 14

What does the suprascapular nerve innervate?

Answer 14

supraspinatus + infraspinatus
bring sensation to acromioclavicular + glenohummeral joints

course: after branching from brahcial plexus, ollow suprascapular artery + vein laterally, posterior to deep trapezius, until superior margin of scapula, passes through scapular notch, enter supraspinous fossa

Question 15

What does the lateral pectoral nerve innervate?

Answer 15

pectorallis major

communicating branch to medial pectral nerve forms loop (ansa pectoralis), branches from medial chord of brachial plexus, pass inferiorly piercing clavicopectoral fascia, pierce deep surface of pectoralis muscle

Question 16

What does the medial pectoral nerve innervate?

Answer 16

pectoralis minor

Question 17

What is the course of the media pectoral nerve?

Answer 17

arises from medial cord of brachial plexus, posteriorly to axillary artery
supplies pectoralis minor + major. Curves anteriorly to lie between axillary artery + vein
receives communicating branch from lateral pectoral nerve (ansa pectoralis)
enters deep surface of pectoralis minor.

Question 18

What are the specificities of the Upper (superior) subscapular nerve?

Answer 18

smaller than inferior
enters subscapularis fossa
frequently double.

Question 19

What does the Lower (inferior) subscapular nerve supply?

Answer 19

supplies lower part of subscapularis

ends in teres major (sometimes supplied by separate branch)

Question 20

What does the Thoraco-dorsal nerve(C6-C8) supply?

Answer 20

supplies latissimus dorsi.

Question 21

What does the musculocutaneous nerve innervate?

Answer 21

provides sensory innervation to lateral aspect of forearm. (NB.has a varied anatomical course. Can interact with median nerve –> adheres + exchanges fibres)
coracobrachialis, biceps brachii, brachialis muscles

Question 22

What is the course of the musculocutaneous nerve?

Answer 22

arises from anterior division of lateral cord of BP (contains fibers from spinal roots C5, C6 and C7)
leaves axilla
pierces coracobrachialis muscle
passes down arm anterior to brachialis muscle but deep to biceps brachii
innervates both
emerges laterally to biceps tendon
continues into forearm as lateral cutaneous nerve

Question 23

What are pathologies associated with the musculocutanous nerve?

Answer 23

well protected within axilla: most common cause stab wound to axilla region.

Motor functions: coracobrachialis, biceps brachii, brachialis muscles paralysed. Flexion at shoulder weakened, but can still occur due to pectoralis major. Flexion at elbow also affected, but can still be performed: brachioradialis. Supination of affected limb greatly weakened but produced by supinator muscle.

Sensory functions: Loss of sensation over lateral side of forearm.

Question 24

What does the axillary nerve innervate?

Answer 24

Motor Functions: innervates deltoid muscles (innervated by anterior terminal branch of axillary nerve) + teres minor (rotator cuff –> stabilizes glenohumeral) innervated by posterior terminal branch of axillary nerve

Sensory Functions: via posterior terminal branch after innervation of teres minor–>continues as upper lateral cutaneous nerve of arm–> innervates skin over inferior portion of deltoid (‘regimental badge area’).

Question 25

What does axillary nerve damage lead to?

Answer 25

sensation at regimental badge impaired/absent + paraesthesia (pins and needles) in distribution of axillary nerve. Lesion caused by dislocation of shoulder joint /fracture of surgical neck of humerus. Injury of the axillary nerve-->deltoid atrophy, weakness in abduction from 15 degrees to 90 degrees, loss of cutaneous sensation over lower half of deltoid.

Question 26

What is the quadrangular space and what are its boudaries?

Answer 26

gap in muscles of posterior scapular region: pathway for neurovascular structures to move from axilla to posterior shoulder + arm. Boundaries: SUP: Subscapularis + teres minor // INF: Teres major // LAT: Surgical neck of humerus // MED: Long head of triceps brachii// axillary nerve + posterior circumflex humeral artery pass through space.

Question 27

What is the trajectory of the axillary nerve?

Answer 27

• formed within axillary region, direct continuation of posterior cord of BP, contains fibres from C5+C6 nerve roots. • after formation: axillary nerve posterior to axillary artery + anterior to subscapularis descends to inferior border of subscapularis muscle exits axilla posteriorly via quadrangular space. Followed by posterior circumflex humeral artery.

Question 28

What is the trajectory of the median nerve?

Answer 28

• Originates from BP in axilla descends down arm lateral to brachial artery Halfway down arm: crosses over brachial artery becomes situated medially enters anterior compartment of forearm via cubital fossa. • Before entering cubital fossa innervates: pronator teres, Flexor carpi radialis, Palmaris longus, flexor digitorum superficialis In cubital fossa: nerve medial to brachial artery-> enters forearm between humeral + ulnar heads of pronator teresthere: anterior interosseous branch (supplies deep muscles in anterior forearm) given off courses along anterior elbow through 2 heads of pronator teres into forearm beneath edge of fibrous arch of flexor digitorum superficialis in forearm between flexor digitorum profundus + flexor digitorum superficialis enters hand via carpal tunnel terminates by dividing into 2 branches:

Question 29

What are the 2 branches of the median nerve and what do they innervate?

Answer 29

Recurrent branch (Innervates thenar muscles: Abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) Palmar digital branch (Inner fingertips of lateral three and half digits + distal phalanges of same fingers on dorsal side of hand. Also innervates lateral two lumbrical muscles)

Question 30

What is the carpal tunnel and how is it related to the median nerve?

Answer 30

formed by carpal bones (floor), transverse carpal ligament (roof), scaphoid + trapezium (radial side), pisiform + hook of the hamate (ulnar side). Median nerve subdivides into digital + muscular branches (recurrent branch) when exiting carpal tunnel.

Question 31

How is the Palmar branch (distal branch) of the median nerve formed?

Answer 31

released before entering retinaculum flexorum.

Question 32

What is the Anterior interosseous nerve formed from the medial nerve?

Answer 32

branches posteriorly from median nerve between two heads of pronator teres: proximal, deep branch, innervates deep flexors.

Question 33

What is the trajectory of the radial nerve?

Answer 33

• Roots: C5-T1, arises in axillary region (situated posteriorly to axillary artery) exits axilla inferiorly (via triangular interval)supplies branches to long + medial heads of triceps brachii descends down posterior aspect of arm (travels in shallow depression within surface of humerus: radial groove: separates medial and lateral heads of triceps) On lateral side of arm passes anteriorly through lateral intermuscular septum enters anterior compartment lies between brachialis + brachioradialis (posterior comp. of forearm) which attaches to lateral supraepicondylar ridge of the humerus enters forearm anterior to lateral epicondyle of humerus, deep to brachioradialis muscle terminates by dividing into 2 branches:

Question 34

What are the 2 branches arrising from the radial nerve and what do they innervate?

Answer 34

o Deep branch (motor) – innervates most muscles in posterior compartment of forearm. o Superficial branch (sensory) – contributes to cutaneous innervation of hand + fingers

Question 35

The sensory branches of the radial nerve are released in 2 location, where?

Answer 35

* Sensory branches released in upper arm (AXILLA)-->Posterior cutaneous nerve of the arm * Sensory branches released in SPIRAL GROOVE -->Lower cutaneous nerve of arm + Posterior cutaneous nerve of forearm

Question 36

What accompanies the radial nerve during its course in the upper arm?

Answer 36

During course in upper arm: accompanied by deep branch of brachial artery.

Question 37

What is the triangular interval?

Answer 37

formed by shaft of humerus, inferior margin of teres major muscle, lateral margin of long head of triceps bracchi.

Question 38

What are the motor functions of the radial nerve?

Answer 38

Innervates triceps brachii, extensor muscles in posterior compartment of forearm. In upper arm, innervates 3 heads of triceps brachii (acts to extend arm at elbow). Also gives rise to branches that supply brachioradialis + extensor carpi radialis longus (posterior forearm). Terminal branch of radial nerve, deep branch, innervates remaining muscles of posterior forearm. These muscles act to extend at wrist + finger joints, supinate forearm.

Question 39

When deep branch of radial nerve penetrates supinator muscle of forearm, it is called the _____________

Answer 39

posterior interosseous nerve.

Question 40

What are the sensory functions of the radial nerve?

Answer 40

Innervates posterior aspect of arm + forearm + the posterior lateral aspect of hand. Superficial branch (sensory) in antero-lateral aspect of forearm deep to brachioradialis + contributes to cutaneous innervation of hand + fingers.

Question 41

What does a lesion in the axilla region of the radial nerve lead to ?

Answer 41

radial nerve damage by dislocation at shoulder joint/fracture of proximal humerus. Occa. injured via excessive pressure on nerve within axilla (eg. badly fitting crutch). o Motor functions: triceps brachii + muscles in posterior compartment affected--> patient unable to extend at elbow, wrist, fingers. UNOPPOSED FLEXION OF WRIST OCCURS, KNOWN AS WRIST-DROP. o Sensory functions: all 4 cutaneous branches of radial nerve affectedloss of sensation over lateral + posterior upper arm, posterior forearm, dorsal surface of lateral three and a half digits.

Question 42

What does a lesion in the spinal grove of the radial nerve lead to ?

Answer 42

• In Radial Groove radial nerve tightly bound within spiral groove of humerus--> susceptible to damage with a fracture of humeral shaft. o Motor functions: triceps brachii weakened, but not paralysed (branches to long + medial heads of triceps arise proximal to radial groove).Muscles of posterior forearm mainly affected -->patient unable to extend at wrist + fingers --> unopposed flexion of wrist occurs, known as wrist-drop. o Sensory functions: cutaneous branches to arm already arisen --> superficial branch of radial nerve damaged --> sensory loss on dorsal surface of lateral 3 and half digits + associated palm area.

Question 43

What is the trajectory of the ulnar nerve?

Answer 43

• posteromedial to brachial artery in anterior compartment of upper 1/2 arm pierces medial intermuscular septum at arcade of Struthers, medial to the triceps At elbow passes posterior to medial epicondyle(nerve easily palpable +vulnerable to injury) enters forearm passes through cubital tunnel in forearm passes between 2 heads of flexor carpi ulnaris travels alongside ulna, lying over flexor digitorum profundus there: gives off 3 branches: muscular branches (proximal) +palmar cutaneuos branch + dorsal cutaneous branch (distal) 5 cm proximal to wrist releases Palmar cutaneous branch (innervates skin of medial half of palm) + Dorsal cutaneous branch (arises 5 cm. proximal to wrist + provides sensory innervation to medial portion of IV and all Vth finger)

Question 44

3 branches of the ulnar nerve arise in the forarm, what are their names?

Answer 44

muscular branch superficial terminal branch deep branch

Question 45

What does the msucular branch of the ulnar nerve innervate?

Answer 45

innervates 2 muscles in anterior compartment of forearm (FLEXOR CARPI ULNARIS + FLEXOR DIGITORUM PROFUNDUM).

Question 46

What is the trajectory of the muscular branch of the ulnar nerve?

Answer 46

• At wrist ulnar nerve travels superficially to FLEXOR RETINACULUM enters hand via ulnar canal (or Guyon’s canal: fascia, superficial part of flexor retinaculum, which bridges over ulnar neurovascular bundle + attaches to radial side of pisiform tunnel occasional site of ulnar nerve entrapment) finishes in hand superficial + deep branch:

Question 47

What does the superficial terminal branch of the ulnar nerve supply?

Answer 47

supplies palmaris brevis + medial palmar skin

Question 48

What is the trajector of the superficial terminal branch of the ulnar nerve?

Answer 48

Divides into 2 palmar digital nerves (supply medial side of little finger) + common palmar digital nerve (sends twig to median nerve + divides into 2 proper digital nerves to supply adjoining sides of little + ring fingers.) Proper digital branches distributed like those derived from median nerve.

Question 49

What does the deep branch of the ulnar nerve innervate?

Answer 49

muscles of hypothenar eminence + intrinsic muscles of hand

Question 50

How does the ulnar nerve innervate the hand?

Answer 50

majority of intrinsic hand muscles innervated by deep branch of ulnar nerve. Hypothenar muscles (Flexor digiti minimi brevis, abductor digiti minimi, opponens digiti minimi): group of muscles associated with little finger innervated by the ulnar nerve also innervates medial two lumbrical + interossei of the hand + adductor pollicis + palmaris brevis

Question 51

What is the cubital tunnel?

Answer 51

space through which ulnar nerve passes posterior to medial epicondyle of humerus.

Question 52

What are the boundaries of the cubital tunnel?

Answer 52

Roof: cubital tunnel retinaculum (ligament of Osborne), extends from olecranon to medial epicondyle anconeus epitrochlearis (when present) Lateral wall: olecranon process Medial wall: medial epicondyle Floor: elbow joint capsule, posterior band of medial collateral ligament of elbow joint

Question 53

What are the 3 pathologies associated with the ulnar nerve?

Answer 53

* narrowing of scalene space by cervical rib: pain irradiating along arm + circulatory impairment * thoracic outlet syndrome: thoracic outlet compressed area: impingement between rib and clavicle * costoclavicular syndrome: narrowing of costoclavicular space.