Median Nerve:
The median nerve originates from lateral and medial cords of the brachial plexus.
- Lateral root arises from the anterior divisions of superior and middle trunks, has contributions from ventral roots of C5-C7
- Medial root arises from the anterior division of the inferior trunk and has contributions from ventral roots of C8-T1
It is one of the five main nerves originating from the brachial plexus.
Course of the Median Nerve
- Median nerve continues down the arm with brachial artery, when it initially lies lateral to the artery, and later crosses over to lie medial to it around halfway down the arm
- Next, it passes within medial part of the antecubital fossa within the two heads of the pronator teres muscle
- Then it goes through anterior forearm within flexor digitorum superficialis and flexor digitorum profundus muscles and performs three branches:
Anterior interosseous nerve – descends simultaneously the anterior interosseous membrane with the anterior interosseous artery.
Deep branch – penetrates into hand through the carpal tunnel beneath flexor retinaculum of the wrist, within the flexor carpi radialis and the flexor digitorum superficialis tendons.
Superficial/palmar cutaneous branch – while arises just before the wrist and pierces carpal ligament to penetrate the carpal tunnel – this nerve is therefore not affected by carpal tunnel syndrome.
Sensory Supply of the Median Nerve
- The median nerve provides none sensory innervation to the upper arm
- The skin over the thenar eminence
- The lateral ⅔ palm of the hand
- The palmar aspect of lateral 3½ fingers
- The dorsal fingertips of lateral 3½ fingers (thumb, index, middle and half of the ring finger)
Motor Supply of the Median Nerve
- The median nerve provides none motor supply to the axilla or upper arm
- Median nerve supply all muscles of the anterior compartment of forearm except the flexor carpi ulnaris muscle and medial two parts of flexor digitorum profundus muscle
- Flexor carpi radialis muscle—flexes and abducts the wrist
- Pronator teres and pronator quadratus muscle – pronation of the forearm
- Palmaris longus muscle – flexion of the wrist and tenses palmar aponeurosis
- Lateral two parts of flexor digitorum profundus muscle – flexes the index and the middle fingers at DIPJs
- Flexor digitorum superficialis muscle – flexion of the fingers at PIPJs
- Flexor pollicis longus muscle – flexes the thumb at IPJ
- Intrinsic muscles of hand – LOAF muscles
- Lateral two lumbricals muscle – flexes the MCPJs and extend the IPJs of the index and middle finger
- Opponens pollicis muscle – opposes the thumb
- Abductor pollicis brevis muscle – abducts the thumb
- Flexor pollicis brevis muscle– flexes the thumb at MCPJ
Common Median nerve injuries
- Compression by the carpal tunnel syndrome
- Stab wounds to antecubital fossa, the forearm of the wrist
- Supracondylar fractures of the humerus
Upper Extremity Muscle Atlas
- Abductor Pollicis Longus
- Abductor Digiti Minimi
- Abductor Pollicis Brevis
- Adductor Pollicis
- Anconeus
- Biceps Brachii
- Brachioradialis
- Brachialis
- Coracobrachialis
- Deltoid
- Extensor Carpi Radialis Longus
- Extensor Carpi Radialis Brevis
- Extensor Carpi Ulnaris
- Extensor Digitorum
- Extensor Digiti Minimi
- Extensor Indicis
- Extensor Pollicis Longus
- Extensor Pollicis Brevis
- Flexor Carpi Radialis
- Flexor Carpi Ulnaris
- Flexor Digitorum Profundus
- Flexor Digitorum Superficialis
- Flexor Digiti Minimi Brevis
- Flexor Pollicis Brevis
- Flexor Pollicis Longus
- Infraspinatus
- Interosseous Muscles, Dorsal
- Interosseous Muscles, Palmar
- Levator Scapulae
- Latissimus Dorsi
- Opponens Digiti Minimi
- Opponens Pollicis
- Pectoralis Major
- Pectoralis Minor
- Palmaris Longus
- Pronator Quadratus
- Pronator Teres
- Rhomboid Major and Minor
- Subscapularis
- Supinator
- Serratus Anterior
- Supraspinatus
- Trapezius
- Triceps Brachii
- Teres Major
- Teres Minor