Innervation of the Upper Limb Flashcards
glenohumeral joint
joint between humerus and scapula
radius vs ulna
radial is more lateral (thumb side)
ulna is more medial (pinky side)
joints of the hand
CMC: carpometacarpal joint
MCP: metacarpophalangeal joint
PIP: proximal interphalangeal joint
DIP: distal interphalangeal joint
what is the brachial plexus
relations
divisions
somatic plexus formed by the ventral rami of C5 to T1
closely related to axillary artery and vein
divided into roots, trunks (neck), divisions (behind clavicle), cords (in axilla), and terminal nerves
terminal branches of the brachial plexus
musculocutaneous nerve
axillary nerve
median nerve
ulnar nerve
radial nerve
what is the musculocutaneous nerve is a branch of
lateral cord of the brachial plexus (C5-7)
musculocutaneous nerve pathway and motor supply
passes through coracobrachialis muscle and descends between biceps brachii and brachialis muscle in the front of the arm
motor supply to flexor compartment of the arm (above muscles), flexion of shoulder and elbow joints
musculocutaneous nerve sensory supply and pathway
continues into the forearm anterior to elbow and becomes lateral cutaneous nerve of forearm
sensory supply to the skin on the lateral forearm
result of damage to musculocutaneous nerve
biceps jerk reflex (C5, C6)
no contraction of flexor compartment of arm
hitting the distal attachment of the biceps triggers contraction of flexor and relaxation of extensor of arm
what is the axillary nerve a branch of
posterior cord of the brachial plexus (C5, C6)
axillary nerve pathway
exits the axilla posteriorly and passes posteriorly around the surgical neck of the humerus
axillary nerve motor supply and function
deltoid and teres minor muscles
abduction, flexion, extension and external rotation of shoulder
axillary nerve sensory supply
skin over the deltoid (regimental patch) via the superior lateral cutaneous nerve
effect of injury to axillary nerve
when is this common
paralysis of deltoid and weakness of abduction of arm
sensory loss over deltoid
may occur when surgical neck of humerus is fractured
what is the median nerve a branch of
lateral cord and medial cord of the brachial plexus (C5-T1)
median nerve general pathway
extend from the terminal branches of the brachial plexus distally to the hand
median nerve motor supply and pathway
no motor supply to the arm
supplies forearm and hand
descends on the antero-medial aspect of the arm with no branches
at the cubital fossa (elbow region) it is located anterior to the brachialis muscle and medial to the brachial artery
passes into the forearm and supplies all muscles except the 1.5 supplied by ulnar nerve
passes through carpal tunnel and supplies muscles of the hand
forearm muscles supplied by median nerve
pronator teres
superficial flexor muscles
flexor digitorium superficialis (FDS)
flexor pollicis longus (FPL)
lateral half of flexor digitorium profundus (FDP)
carpal tunnel
fibrous tunnel formed by the flexor retinaculum and the wrist bones
median nerve passes though inside it
ulnar nerve passes superficially to it
hand muscles supplied by the median nerve and their role
thenar muscles for thumb abduction and flexion
median nerve sensory supply
lateral part of palm
palmar surface and nailbeds of the lateral 3 and half digits
median nerve effect of injury and common causes
motor loss of pronation of forearm, opposition of thumb, flexion of index and middle fingers, hand of Benediction when attempting to make a fist
weakness of abduction and flexion of thumb and sensory loss over lateral three digits palmar surface
causes by fracture of distal humerus or carpal tunnel syndrome
what is the ulnar nerve a branch of
medial cord of the brachial plexus (C7-T1)
ulnar nerve pathway and motor supply
descends along the medial aspect of the arm
passes behind medial epicondyle of the humerus
passes into the medial side of the forearm and supplies 1 and a half muscles in forearm
passes superficially to the carpal tunnel and supplies muscles of the hand
forearm muscles supplied by ulnar nerve
flexor carpi ulnaris (FCU)
medial half of flexor digitorium profundus (FDP)
hand muscles supplied by the ulnar nerve and their role
three hypothenar muscles
abduct and flex 5th finger allowing opposition of fingers
ulnar nerve effect of injury
claw hand deformity (flexed at PIP and DIP, extended at MCP)
loss of adduction of thumb and sensory loss over medial 1 and a half fingers and part of the hand
why is the radial nerve the most commonly injured
largest nerve in the upper limb
long course
proximity to the humeral shaft
what is the radial nerve a branch of
posterior cord of the brachial plexus (C5-T1)
radial nerve pathway and motor supply in arm
descends posteriorly between the three heads of the triceps brachii
supplies the triceps brachii
passes behind the spiral (radial) groove on the back of the humerus
enters laterally to the anterior compartment of the arm between the brachialis and brachioradialis muscles
supplies the brachioradialis muscle
radial nerve pathway and motor supply in forearm
enters the forearm anterior to the lateral epicondyle of humerus
divides into deep (motor) and superficial (sensory) branches
deep branch enters posterior compartment of the forearm
radial nerve sensory supply of arm
supplies skin of the posterior surface of the arm via posterior cutaneous nerve (arises from axilla)
supplies skin of lower lateral arm and posterior of forearm via interior lateral cutaneous nerve and posterior cutaneous nerve respectively
radial nerve sensory supply of forearm
superficial branch descends on the anterolateral aspect under brachioradialis muscle
passes dorsally to the back of the hand and supplies the lateral side and back of the hand and back of the lateral 3 and a half digits (excluding nailbeds)
radial nerve effects of injury
sensory loss posterior of arm, forearm, dorsolateral surface of hand and dorsal or lateral 3 and a half digits
injury at axilla (crutch palsy) - inability to extend elbow
injury at spiral groove (Saturday night palsy) - wrist drop
