Median, Ulnar and Radial Nerve – Course and Innervation

Median nerve, Ulnar nerve and Radial nerve are the 3 major nerves of the upper limb originating from the brachial plexus.

Some important neuroanatomic relationships in the forearm are:

1. Medial nerve: Crossed by brachial artery from lateral to medial just above the elbow to lie medial to brachial artery in cubital fossa.

2. Anterior interosseous nerve: Splits pronator teres and runs between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP).

3. Ulnar nerve: Between flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP).

4. Radial nerve: Between brachialis and brachioradialis.

5. Posterior interosseous nerve: Splits supinator

peripheral nerves upper limb

Course and innervation of these nerves have been simplified and tabulated below:

Part of upper limbUlnar nerveSupplyMedian nerveSupplyRadial nerveSupply
OriginMedial cord (C8-T1)Lateral and Medial cord (C5-T1)Posterior cord (C5-T1)
AxillaMedial to axillary arteryNoneLateral to axillary arteryNoneBehind axillary artery – exits axilla via Triangular intervalLong and medial head of triceps

Posterior cutaneous nerve of arm
Proximal armMedial to brachial arteryNoneLateral to brachial arteryNonePosterior compartment (Spiral groove – from medial to lateral)Lateral head of triceps and Anconeus

Lateral cutaneous nerve of arm and Posterior cutaneous nerve of forearm

Distal armPosterior compartment (over medial head of triceps) after piercing medial intermuscular septumNoneAnterior compartment (Crosses brachial artery from lateral to medial at coracobrachialis insertion) – runs under bicepsNoneAnterior compartment (Pierces lateral intermuscular septum ~10 cm proximal to lateral epicondyle) – in front of lateral epicondyle between Brachialis and BR/ECRLBrachialis
ElbowPasses behind medial epicondyle (cubital tunnel)Elbow jointCubital fossa (Medial to brachial artery; Beneath lacertus fibrosus)Elbow jointDivides
ForearmEnters between 2 heads of FCUFCUEnters between 2 heads of PT

PTSBRN – sensory (travels under BR and emerges between BR and ECRL ~8 cm proximal to radial styloid)
Travels between FCU and FDPUlnar 2 FDPsBranches to anterior compartment muscles of forearm
PL, FCR, FDSDBRN (passes through FREAS)
-Fibrous bands
– Radial neck (radial recurrent vessels)
– Arcade of Frohse (supinator arch)
-Supinator (distal border)
Palmar cutaneous branchHypothenar skinAnterior interosseous nerve – runs between FDP and FPLPQ, FPL, lateral 2 FDPDBRN emerges out of Radial tunnel/FREAS as PINSupinator and all 6 muscles of extensor compartment
Dorsal cutaneous branchDorsal aspect of medial 1 & 1/2 fingers and associated hand areaTravels down forearm entering 2 heads of FDS (sublimis bridge) and runs between FDS and FDP
Runs between FCR and PL (gives palmar cutaneous branch)Thenar eminence sensory
Wrist and HandPasses superficial to flexor retinaculum and travels under piso-hamate ligament (Guyon’s canal)Passes deep to carpal tunnel (flexor retinaculum)SBRN runs as dorsal radial sensory nerve crossing anatomical snuff box lateral to radial arteryWrist, Dorsal lateral 3 and 1/2 fingers upto distal interphalangeal joint and corresponding dorsum of hand
a.Superficial branch (sensory)Palmar surface of medial 1 & 1/2 fingers

Palmaris brevis
Palmar digital branchPalmar surface and fingertips of lateral 3 and 1/2 digits

1st and 2nd lumbricals

b.Deep branch (motor)1 & 1/2 thenar muscles – Adductor pollicis, deep head of FPB

All hypothenar muscles except palmaris brevis

All interossei

2 Lumbricals (3rd, 4th)
Recurrent thenar branchThenar muscles (AbPB, OP, Superficial head of FPB)

Further reading:

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