Applied Anatomy: Brachial Plexus

brachial plexus organization

• formed by nerve roots C5. C6, C7, C8, and T1

• nerve roots become nerve trunks

  • upper - C5 and C6

  • middle - C7

  • lower - C8 and T1

• nerve trunks branch into anterior and posterior divisions

  • anterior divisions generally innervate flexors

  • posterior divisions generally innervate extensors

lateral cord

anterior divisions of upper and middle trunks

medial cord

anterior divisions of lower trunk

posterior cord

divisions of upper, middle, and lower trunk

divisions come together to form…

cords

primary nerves

• long thoracic nerve

• dorsal scapular nerve

long thoracic nerve

• origin: nerve root C5, C6, and C7

• motor: serratus anterior muscle

• sensory: none

• interest: scapular winging

serratus anterior muscle

• origin: superior aspect of the first eight ribs

• insertion: anterior/medial border of the scapula

• function: protraction of the scapula

dorsal scapular nerve

• origin: nerve root C5

• motor: rhomboid minor, rhomboid major, levator scapulae

• sensory: none

• interest: rhomboid weakness (posture)

Primary nerves of the arm

• suprascapular nerve

• axillary nerve

• musculocutaneous nerve

• median nerve

• ulnar nerve

• radial nerve

suprascapular nerve

• origin: upper trunk of brachial plexus

• motor: supraspinatus muscle, infraspinatus muscle

• sensory: posterior joint capsule of gleenohumeral joint

• interest: weak rotator cuff

infraspinatus

• origin: infraspinous

• insertion: greater tubercle of humerus

• function: external rotation humerus

supraspinatus

• originate: supraspinous fossa Scapula

• insertion: superior greater tubercle humerus

• function: initiates abduction humerus

axillary nerve

• origin: posterior cord

• motor: deltoid muscle, teres minor

• sensory: lateral shoulder

deltoid muscle

• originate: lateral 3rd clavicle, acromion process, spine of scapula

• insertion: deltoid tuberosity

• function: glenohumeral abduction

teres minor

• originate: lateral-dorsal border of scapula

• insertion: greater tubercle (inferior aspect) of Humerus

• function: external rotation of humerus

musculocutaneous nerve

• origin: lateral cord

• motor: biceps brachii

• sensory: lateral forearm

biceps brachii

• originate: short→coracoid process scapula, long→supra-glenoid lop of fossa

• insertion: radial tuberosity…interosseous membrane

• function: flexes and supinates forearm

median nerve

• lateral cord & medial cord

• motor: flexors of forearm

• sensory: palmer aspects of digits 1-3, ½ palmer lateral aspect of digit 4, dorsal aspect of DIP digits 1-3, radial ½ DIP digit 4

• interest: carpal tunnel

flexors carpi radialis

• originate: medial epicondyle of Humerus

• insertion: proximal base of 2nd and 3rd metacarpals

• function: flexion of the wrist

ulnar nerve

• origin: medial cord

• motor: flexor digiti minimi

• sensory: medial aspect of forearm and hand, 5th digit and ulnar ½ of the 4th digit

flexor digiti minimi

• origination: hook of the hamate

• insertion: medial aspect of the proximal phalanx 5th digit

• function: flexes proximal phalanx (MCP) of the 5th digit

radial nerve

• origin: posterior cord

• motor: triceps, extensor carpi radialis

• sensory: dorsum thumb (to IP articulation), ulnarward to radial aspect of 4th digit dorsum

triceps brachii

• origination:

  • long head: inferor aspect of glenoid fossa

  • lateral head: posterior proximal shaft of humerus

  • medial head: posterior humeral shaft

• insertion: common tendon olecranon process