Ulnar nerve
The ulnar nerve is one of the terminal branches of the brachial plexus and has motor and sensory supply to the forearm and hand.
On this page:
Gross anatomy
Origin
The ulnar nerve originates as a terminal branch of the medial cord of the brachial plexus with nerve root fibers from C8-T1.
Course
Arm
In the arm, the ulnar nerve runs medial to the axillary artery and subsequently the brachial artery on the coracobrachialis muscle in the anterior compartment. The nerve passes to the posterior compartment through the medial intermuscular septum distally running with the superior ulnar collateral artery. Further on, it runs between medial head of triceps brachii muscle and the medial intermuscular septum to pass posterior to the medial humeral epicondyle in the superficial condylar groove (cubital tunnel).
Forearm
The ulnar nerve enters the forearm from the arm via the two heads of flexor carpi ulnaris (FCU) muscle. It subsequently lies superficial to flexor digitorum profundus and deep to FCU and medial to the ulnar artery. At the wrist, the ulnar nerve runs lateral to the tendon of FCU.
Hand
The ulnar nerve enters the hand superficial to the flexor retinaculum and inside Guyon's canal. Then it divides into its terminal branches at the level of the pisiform bone.
Prior to passing the flexor retinaculum at the wrist, the ulnar nerve gives off the dorsal cutaneous branch.
Branches
Terminal branches
- dorsal cutaneous branch
- palmar cutaneous branch
- branch to palmaris brevis
- superficial terminal branch
- deep terminal branch
Supply
The ulnar nerve has both sensory and motor supply:
- motor
- flexor carpi ulnaris
- flexor digitorum profundus (medial half)
- hypothenar muscles (abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi)
- 3rd and 4th lumbricals
- palmar and dorsal interossei muscles
- flexor pollicis brevis (deep head)
- adductor pollicis
- palmaris brevis
- sensory
- articular innervation to elbow, wrist, carpal and phalangeal joints
- cutaneous innervation to ulnar aspect of the hand, specifically the 5th digit and the medial half of the 4th digit.
Variant anatomy
- may arise from the 7th and/or 8th cervical nerve roots only
- may pass in front of the medial epicondyle of the distal humerus
- Riche-Cannieu anastomosis: communication between the recurrent branch of median nerve and deep branch of ulnar nerve in hand
- Martin-Gruber anastomosis: communicating nerve branch between the median nerve and the ulnar nerve in the forearm
- may supply all the thenar muscles
- branch to the dorsum may be absent
Related pathology
Related Radiopaedia articles
Anatomy: Upper limb
-
skeleton of the upper limb
- clavicle
- scapula
- humerus
- radius
- ulna
- carpal bones (mnemonic)
- metacarpals
- phalanges
- accessory ossicles of the upper limb
- accessory ossicles of the shoulder
- accessory ossicles of the elbow
-
accessory ossicles of the wrist (mnemonic)
- os centrale carpi
- os epilunate
- os epitriquetrum
- os styloideum
- os hamuli proprium
- lunula
- os triangulare
- trapezium secondarium
- os paratrapezium
- os radiostyloideum (persistent radial styloid)
- joints of the upper limb
-
pectoral girdle
-
shoulder joint
- articulations
- associated structures
- joint capsule
- bursae
- ligaments
-
movements
- scapulothoracic joint
- glenohumeral joint
- arm flexion
- arm extension
- arm abduction
- arm adduction
- arm internal rotation (medial rotation)
- arm external rotation (lateral rotation)
- circumduction
- blood supply - scapular anastomosis
- ossification centers
-
shoulder joint
-
elbow joint
- proximal radioulnar joint
- ligaments
- associated structures
- movements
- alignment
- blood supply - elbow anastomosis
- development
-
wrist joint
- articulations
-
ligaments
- intrinsic ligaments
- extrinsic ligaments
- radioscaphoid ligament
- dorsal intercarpal ligament
- dorsal radiotriquetral ligament
- dorsal radioulnar ligament
- volar radioulnar ligament
- radioscaphocapitate ligament
- long radiolunate ligament
- Vickers ligament
- short radiolunate ligament
- ulnolunate ligament
- ulnotriquetral ligament
- ulnocapitate ligament
- ulnar collateral ligament
- associated structures
- extensor retinaculum
- flexor retinaculum
- joint capsule
- movements
- alignment
- ossification centers
-
hand joints
- articulations
- carpometacarpal joint
-
metacarpophalangeal joints
- palmar ligament (plate)
- collateral ligament
-
interphalangeal joints
- palmar ligament (plate)
- collateral ligament
- movements
- ossification centers
- articulations
-
pectoral girdle
- spaces of the upper limb
- muscles of the upper limb
- shoulder girdle
- anterior compartment of the arm
- posterior compartment of the arm
- anterior compartment of the forearm
-
posterior compartment of the forearm (extensors)
- superficial
- deep
- hand (mnemonic)
- accessory muscles
- blood supply to the upper limb
-
arteries
- subclavian artery (mnemonic)
- axillary artery
- brachial artery (proximal portion)
- ulnar artery
- radial artery
- veins
-
arteries
- innervation of the upper limb
- intercostobrachial nerve
-
brachial plexus (mnemonic)
- branches from the roots
- branches from the trunks
- branches from the cords
- lateral cord
- posterior cord
- medial cord
- terminal branches
- lymphatic drainage of the upper limb