Author: Shahab Shahid MBBS•Reviewer: Uruj Zehra MBBS, MPhil, PhDLast reviewed: October 14, 2021Reading time: 13 minutes
The ulnar nerve is a terminal branch of the medial cord the the brachial plexus. It includes mainly yarn from the anterior rami of spinal nerves C8 and T1, yet may sometimes carry C7 fibers together well.
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From that origin, the ulnar nerve courses distally with the axilla, arm and also forearm right into the hand. It is a mixed nerve and also provides motor innervation to assorted muscles that the forearm and hand and also sensory supply to the skin that the hand.
The ulnar nerve can extensively be explained as the nerve of the hand, as it innervates the vast bulk of the intrinsic hand muscles. It is one of the many clinically pertinent nerves of the upper limb, as result of its superficial course and also clinically apparent function in hand function.
This write-up will discuss the anatomy and function of the ulnar nerve, and also its clinical relevance.
|Origin||Brachial plexus (C8-T1)|
|Branches||Muscular branches, articular branches, palmer cutaneous branch, dorsal cutaneous branch, superficial branch, deep branch|
|Supply||Motor: - Flexor carpi ulnaris and also medial fifty percent of flexor digitorum profundus- most of the intrinsic hand musclesSensory: - Anterior aspect of the ulnar 1½ finger (little finger and half of the ring finger) and medial palmar skin- Dorsal aspect of the ulnar 1½ fingers and medial facet of dorsum the hand|
|Mnemonic||Ulnar nerve gives all intrinsic muscle of the hand except the LOAF muscles.(standing for: Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)|
Origin and also course Branches and innervationClinical relations
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Origin and also course
The ulnar nerve is the distal continuation of the medial cord the the brachial plexus, from the nerve root of C8 and T1. It frequently carries yarn from C7 via a communicating branch native the lateral cord.
From the medial cord, the ulnar nerve passes distally v the axilla, medial come the axillary artery. It descends top top the medial aspect of the arm, medial come the brachial artery and the biceps brachii muscle. In the mid-portion of the arm, the nerve pierces the medial intermuscular septum to get in the posterior compartment. Here, the nerve runs anterior come the medial head the triceps barchii muscle and also in 70-80% of people, this nerve overcome under the arcade of Struthers. This is a thin, aponeurotic band, the extends native the medial head of triceps come the medial intermuscular septum.
The ulnar nerve then passes between the medial epicondyle and olecranon in the groove because that ulnar nerve to enter the anterior compartment the the forearm. Posterior to the medial epicondyle, the ulnar nerve is subcutaneous and also easily palpable. It is generally referred to together the "funny bone" in this region. The ulna nerve generally has no branches in the arm.
From the arm, the ulnar nerve runs v the cubital tunnel, superficial to the posterior and also oblique bands of the ulnar collateral ligament. This cubital tunnel is bordered by the medial epicondyle, the olecranon and also a fibrous band (arcuate ligament) which joins the two heads the flexor carpi ulnaris muscle. Here, the nerve provides off articular branches come the elbow joint. The ulnar nerve proceeds into the anterior compartment the the forearm by passing between the humeral and ulnar heads of the that flexor carpi ulnaris.
The ulnar nerve descends on the medial facet of the forearm, over the flexor digitorum profundus muscle and deep come the flexor carpi ulnaris muscle. Close to the wrist, the nerve emerges lateral come flexor carpi ulnaris v the accompanying ulnar artery, i beg your pardon lies lateral to it. Both structures run superficial come the flexor retinaculum (transverse carpal ligament) to go into the hand simply lateral come the pisiform bone and also are just covered by fascia and skin.
In the forearm, the ulnar nerve offers rise to 2 muscular branches: one to the flexor carpi ulnaris and the second to the ulnar (medial) component of the flexor digitorum profundus. The lateral fifty percent of the flexor digitorum profundus muscle and also the staying muscles that the anterior compartment of the forearm are supplied by the average nerve. Additionally, the ulna nerve provides rise to 2 cutaneous branches in the forearm: palmar cutaneous nerve and dorsal cutaneous nerve. This nerves pass into the hand to administer sensory innervation.
At the wrist, the ulnar nerve and also artery go into the hand through coursing through the Guyon’s canal (ulnar canal), a groove between the pisiform and the hook that the hamate, linked by the palmar carpal ligament. Here, the nerve divides into superficial and deep branches to administer both sensory and also motor innervation come the hand.
Branches and innervation
The ulnar nerve normally does not have actually any major branches in the arm. In the forearm the nerve offers rise come articular branches, muscular branches, and also the palmar and dorsal cutaneous branches. In the hand, the nerve provides two terminal branches: superficial branch of ulnar nerve and also deep branch that ulnar nerve.
As the ulnar nerve passes between the medial epicondyle and also olecranon and also through the cubital tunnel, it gives rise to articular branches that provide innervation come the elbow joint.
Two muscular branches arise from the ulnar nerve in the proximal forearm. This supply motor innervation to the flexor carpi ulnaris and also the medial fifty percent of the flexor digitorum profundus.
Palmar cutaneous branch
The palmar cutaneous branch occurs from the ulnar nerve roughly the mid-portion the the forearm. This nerve runs follow me the ulnar artery to the distal forearm, whereby it perforates the deep fascia. It provides sensory innervation come the skin at base of the medial palm, i m sorry overlies the medial carpal bones.
Dorsal cutaneous branch
The dorsal cutaneous branch of the ulnar nerve increase in the distal forearm, proximal come the wrist. This nerve process posteriorly, deep come the flexor carpi ulnaris and perforates the deep fascia to go into the medial element of the dorsum the hand. Here, that divides into two or three dorsal digital nerves to it is provided sensation come the skin on the medial side of the dorsum of hand and also the proximal regions of the medial 1½ digits (little finger and half of the ring finger).
Superficial branch the ulnar nerve
The superficial branch the the ulnar nerve provides sensory innervation to the anterior facet of the ulnar 1½ number (little finger and half of the ring finger) and also medial palmar skin. Additionally, it gives motor innervation come the palmaris brevis muscle in the hypothenar an ar of the hand. It occurs from the ulnar nerve just distal come the pisiform bone and also often divides right into two palmar digital nerves.
Deep branch that ulnar nerve
The deep branch of the ulnar nerve emerges from the same an ar of the nerve together the superficial branch. That courses in between the muscles of the hypothenar region into the deep element of the plam, alongside the deep palmar branch the the ulnar artery. This nerve offers motor innervation come the vast majority of hand muscles. This include: the hypothenar muscle (abductor, flexor, and also opponens digiti minimi muscles), all the interossei (3 palmar and 4 dorsal), the medial 2 lumbricals, the deep head the flexor pollicis brevis and also adductor pollicis.
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To summarize, the ulnar nerve offers motor innervation to the flexor carpi ulnaris, the medial fifty percent of the flexor digitorum profundus and all the intrinsic hand muscles v the exemption of the LOAF muscles (lateral two lumbricals, opponens pollicis, abductor pollicis brevis and flexor pollicis brevis).
The ulnar nerve gives sensory supply to the following areas of the hand:The skin of the palmar and also dorsal aspects of the medial 1½ number and nearby palm.The skin on the medial next of the dorsum the hand.
Learn an ext about the ulnar nerve and other significant nerves in the upper limb v our video clip tutorials and also quizzes:
It is very easy come remember the innervation provided by the ulnar nerve if you use the following mnemonic:Ulnar nerve provides all intrinsic muscles of the hand except the LOAF musclesLateral two lumbricalsOpponens pollicisAbductor pollicis brevisFlexor pollicis brevi
Ulnar nerve injury
Ulnar nerve injures are rather common and can take place at miscellaneous sites along its course v the top limb. The common sites that injury or compression incorporate posterior come the medial epicondyle, the cubital tunnel and Guyon’s canal. Injures to the ulnar nerve are identified by paresthesia (tingling), numbness and also depending ~ above the severity may an outcome in considerable impairment the both motor and also sensory work in the hand.
The characteristics presentation of one ulnar nerve injury is the "claw hand". People with this deformity have hyperextension of the metacarpophalangeal joints (due to the absence of innervation come the medial two lumbricals and also the unopposed activity of the extensors that this joint) and also flexion the the interphalangeal joints of 4th and 5th fingers (due to the unopposed activity of the flexor digitorum profundus). The severity the this deformity, however, counts on the place of the injury. Greater (proximal) injuries, such as at the elbow, may denervate the ulnar part of flexor digitorum profundus such that the flexed appearance might not be apparent.
Sensory loss following an ulnar nerve injury likewise depends on the site of injury. This is normally determined by assessing the duty of the dorsal cutaneous branch which occurs in the distal forearm and also supplies the medial side of the dorsum the hand.
Usually, the more proximal a nerve injury, the worse it is. Opposing is true as soon as we consider the ulnar nerve. This is due to the fact that the flexor digitorum profundus (in the forearm) the flexes the finger is partly innervated by the nerve. A proximal injury gets rid of innervation to both the forearm muscles and hand muscles. A distal injury, top top the various other hand, only denervates the hand muscles; thus the still functioning finger flexors provide the patience a pronounce clawed figure in the ring and tiny fingers. Through a proximal injury resulting in an open palm, over there is more capacity for hand function. This phenomenon is dubbed the ulnar paradox.
Proximal ulnar nerve compression regularly occurs when a person rests their elbow top top the table for a lengthy time, or top top a window (for lengthy distance drivers). It can also occur together an strong injury, particularly in throwing athletes e.g. Baseball pitchers, cricketers, and javelin throwers. The rapid movement of the elbow share from flexion into whip-like expansion can outcomes in compression that the nerve.
Cyclists regularly suffer ulnar nerve difficulties as they remainder the medial border of their hand on your handlebars, resulting in hamate and therefore distal ulnar nerve compression (handlebar neuropathy).
To aid you remember the hand sign linked with one ulnar nerve injury, usage the adhering to mnemonic.
DR. CUMADrop = Radial nerveClaw = Ulnar nerveMedian nerve = Ape (Apostle"s) hand
References:Chummy S.Sinnatamby: Last’s Anatomy regional and Applied, 12th Edition, Churchill Livingstone Elsevier.Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, second Edition, Churchill Livingstone Elsevier.Elliiot L.Manchell: Gray"s Clinical Neuroanatomy: The Anatomic Basis because that Clinical NeuroscienceMoore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.).Netter, F. (2019). Atlas of human Anatomy (7th ed.). Philadelphia, PA: Saunders.
Illustrators:Forearm (cadaver dissection) - Prof. Carlos Suárez-QuianSensory supply of the skin the the hand - Irina Münstermann, Abdulmalek Albakkar
Ulnar nerve: desire to learn an ext about it?
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