Innervations to the UE muscles

Musculocutaneous Nerve (C5–C7)

Biceps brachii, Brachialis, Coracobrachialis

Biceps brachii:

Flexes the elbow and supinates the forearm.

Brachialis:

Acts as the main flexor of the forearm.

Coracobrachialis:

Flexes and adducts the arm at the shoulder. 

Radial Nerve (C5–T1)

Triceps brachii, Brachioradialis, Anconeus, Extensor carpi radialis longus and brevis, Supinator, Posterior interosseous branch

Triceps brachii:

Extends the elbow joint

Brachioradialis:

Flexes the forearm at the elbow.

Anconeus:

Assists in elbow extension and joint stabilization.

Extensor carpi radialis longus and brevis:

Extend and abduct the wrist.

Supinator:

Supinates the forearm.

Posterior interosseous branch:

Innervates deep forearm extensors including the extensor digitorum, extensor carpi ulnaris, and thumb

Median Nerve (C6–T1)

Pronator teres, Flexor carpi radialis, Palmaris longu, Flexor digitorum superficialis, Anterior interosseous branch, Thenar muscles and lateral lumbricals

Pronator teres

Pronates the forearm.

Flexor carpi radialis:

Flexes and abducts the wrist.

Palmaris longus:

Tenses the palmar fascia and flexes the wrist.

Flexor digitorum superficialis:

Flexes the proximal interphalangeal (PIP) joints.

Anterior interosseous branch:

• Supplies the flexor pollicis longus, pronator quadratus, and lateral half of the flexor digitorum profundus.

Thenar muscles and lateral lumbricals:

Control precision movements of the thumb and lateral digits.

Ulnar Nerve (C8–T1)

Flexor carpi ulnaris, Medial half of flexor digitorum profundus, Intrinsic hand muscles

lexor carpi ulnaris:

Flexes and adducts the wrist.

Medial half of flexor digitorum profundus:

Flexes the distal interphalangeal (DIP) joints of the ring and little fingers.

Intrinsic hand muscles:

Includes the hypothenar eminence, interossei (for finger abduction/adduction), medial lumbricals, and adductor pollicis. 

Axillary, Thoracodorsal, and Scapular Nerves (C5–C8)

Deltoid, Teres minor, Latissimus dorsi, Rhomboids (major and minor) and levator scapulae

Deltoid:

Abducts the arm (via the axillary nerve).

Teres minor:

Externally rotates the arm (via the axillary nerve).

Latissimus dorsi:Extends, adducts, and internally rotates the arm (via the thoracodorsal nerve).

• Extends, adducts, and internally rotates the arm (via the thoracodorsal nerve).

Rhomboids (major and minor) and levator scapulae:

Retract and stabilize the scapula (via the dorsal scapular nerve)