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Upper limb neuroanatomy

Summary of motor nerves

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Summary of cutaneous nerves

Median Nerve

Brief summary - see full notes for more detail

  • Origin
    • C6 – T1
    • Continuation of the medial and lateral cords
  • Motor Functions
    • Flexor muscles in the forearm
    • LOAF - Thenar muscles, Two lateral lumbricals
  • Sensory Functions
    • Palmar cutaneous branch and the digital cutaneous branch
  • Course
    • Axilla
      • Formed at lower border of Axilla by union of medial and lateral cords of the Brachial Plexus
      • Axillary Artery clasped between 2 cords
    • Arm
      • Lies in front of Brachial Artery as it passes distally in arm
      • In the cubital fossa it lies medial to Brachial Artery and posterior to the Bicipital Aponeurosis
    • Forearm
      • Leaves the Cubital Fossa by passing between the 2 heads of Pronator Teres
      • Passes deep to the fibrous arch of Flexor Digitorum Superficialis to run between FDS and FDP in the forearm
      • Two branches
        • Anterior Interosseous Nerve Branch
          • Deep flexor muscles
        • Palmer cutaneous nerve
    • Wrist
      • Passes through the Carpal Tunnel into the hand
      • Gives Muscular (Recurrent) Branch - thener muscles
      • Gives Palmar Digital Branches - cutaneous + 2 x radial Lumbrical muscles

Radial Nerve

Brief summary - see full notes for more detail

  • Origin
    • C5 – T1
    • On of continuing branches of the posterior cord
  • Motor Functions
    • Triceps brachii
    • Muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist and fingers)
  • Sensory Functions
    • Innervates the posterior aspect of the arm and forearm, and the posterolateral aspect of the hand.
  • Course
    • Axilla
      • Crosses lower border of posterior axillary wall lying on the tendon of Latissimus dorsi
      • Passes out of sight through Triangular Interval below
      • Supplies:
        • Triceps
        • Posterior Cutaneous Nerve of the Arm
    • Arm
      • Passes obliquely across back of Humerus from medial to lateral in shallow groove
      • Branch
        • Lateral Cutaneous Nerve of Arm
        • Posterior Cutaneous Nerve of the Forearm
      • Pierces the Lateral Intermuscular Septum to enter anterior compartment
      • Runs towards elbow between Brachialis medially, then Brachioradialis and then Extensor Carpi Radialis Longus laterally
      • Supplies
        • Brachioradialis, Extensor Carpi Radialis Longus, and Lateral part of Brachialis
      • Divides (level of lateral epicondyle
        • Superficial Branch
        • Posterior Interosseous Nerve
    • Forearm
      • Posterior Interosseous Nerve
        • Passes into the extensor compartment of the forearm between the two layers of Supinator
        • Reach the Interosseous Membrane
        • Supplies all extensor muscles
      • Superficial Terminal Branch of Radial Nerve
        • Cutaneous continuation of the main Radial Nerve
        • Runs on the lateral side of the forearm under cover of Brachioradialis
        • Leaves flexor compartment by passing backwards deep to tendon of Brachioradialis
        • Reaches back of the hand
        • Supplies: Radial 2/3 of Dorsum of the Hand and proximal parts of Dorsal surfaces of Thumb and lateral two and a half or three and a half fingers

Ulnar Nerve

Brief summary - see full notes for more detail

  • Origin:
  • Motor Functions
    • Muscles of the hand (apart from the thenar muscles and two lateral lumbricals)
    • Flexor carpi ulnaris
    • Medial half of flexor digitorum profundus.
  • Sensory Functions
    • Innervates the anterior and posterior surfaces of the medial one and half fingers, and associated palm area. Course
  • Axilla
    • Runs down between Axillary Artery and Axillary Vein
  • Arm
    • Run with brachial artery and median nerve on the medial aspect of the arm between the anterior and posterior compartments
    • Pierces the Medial Intermuscular Septum in lower third of arm to enter the posterior compartment
  • Elbow
    • Lies in the retrocondylar groove behind the Medial Epicondyle of Humerus
  • Forearm
    • Passing between the two heads of Flexor Carpi Ulnaris
    • Lies under the Flexor Carpi Ulnaris and on the Flexor Digitorum Profundus - supplies both
      • Ulnar Artery on its radial side
    • Supplies:
      • Flexor Carpi Ulnaris
      • Ulnar Half of Flexor Digitorum Profundus
    • Emerges from behind tendon of Flexor Carpi Ulnaris proximal to the wrist
    • Branches
      • Dorsal cutaneous
      • Palmer cutaneous
  • Wrist
    • Passes across the front of the Flexor Retinaculum lateral to the Pisiform bone in the hand
    • Divides on the Flexor Retinaculum alongside Pisiform bone
      • Superficial Branch - sensory
      • Deep Branch - muscular

Musculocutaneous Nerve

  • Roots
    • C5, C6, C7
  • Course
    • Arises from the lateral cord of the brachial plexus
    • Pierces the coracobrachialis muscle
    • Travels between the biceps brachii and brachialis in the anterior compartment of the arm
    • Emerges at the lateral border of the biceps tendon as the lateral cutaneous nerve of the forearm
    • Continues superficially down the lateral forearm
  • Motor Functions
    • Brachialis
    • Biceps brachii
    • Coracobrachialis muscles
  • Sensory Functions
    • Gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm, and a small lateral portion of the posterior forearm.

Axillary Nerve

  • Roots
    • C5 and C6.
  • Motor Functions
    • Teres minor
    • Deltoid muscles
  • Origin
     - Arises from the posterior cord of the brachial plexus
  • Course
    • Exits the axilla through the Quadrangular space, bounded by:
      • Superior: teres minor
      • Inferior: teres major
      • Medial: long head of triceps
      • Lateral: surgical neck of the humerus
    • Winds around the surgical neck of the humerus deep to the deltoid
    • Divides into anterior and posterior branches
  • Sensory Functions
    • Gives off the superior lateral cutaneous nerve of arm

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