Ulnar nerve

Nervus ulnaris

Arises from the medial cord of the brachial plexus (C8-T1). It passes posterior to the medial epicondyle of the humerus (vulnerable to injury), enters the forearm between the heads of flexor carpi ulnaris, and enters the hand through Guyon's canal.

Тип Nerve
Система органов Nervous
Область тела Forearm
Родительская структура arm nerve
Латинское название Nervus ulnaris
FMA ID 37319

Функция

Provides motor innervation to the hypothenar muscles, interossei, adductor pollicis, and medial two lumbricals. Provides sensory innervation to the medial one and a half digits and corresponding palm area.

Клиническое значение

Ulnar nerve entrapment at the elbow (cubital tunnel syndrome) is the second most common nerve entrapment. Ulnar nerve injury causes claw hand deformity. The funny bone sensation is the ulnar nerve passing posterior to the medial epicondyle.

Часто задаваемые вопросы

What muscles does the ulnar nerve innervate in the hand?
The ulnar nerve provides motor innervation to most of the intrinsic muscles of the hand. These include the hypothenar muscles (abductor digiti minimi, flexor digiti minimi, opponens digiti minimi), all seven interossei (both dorsal and palmar), the medial two lumbricals (for the ring and little fingers), and the adductor pollicis. The ulnar nerve also supplies the flexor carpi ulnaris and the medial half of flexor digitorum profundus in the forearm.
What sensory areas does the ulnar nerve supply?
The ulnar nerve provides sensory innervation to the medial one and a half digits—the little finger (digit 5) and the ulnar half of the ring finger (digit 4)—along with the corresponding area of the palm (hypothenar eminence). On the dorsum of the hand, the dorsal cutaneous branch of the ulnar nerve (which branches above the wrist) supplies the dorsal aspect of the little finger, ring finger, and the ulnar half of the long finger.
What is cubital tunnel syndrome?
Cubital tunnel syndrome is entrapment or compression of the ulnar nerve at the elbow, specifically as it passes through the cubital tunnel—a fibro-osseous channel posterior to the medial epicondyle of the humerus. It is the second most common peripheral nerve entrapment (after carpal tunnel syndrome). Patients experience numbness and tingling in the ring and little fingers, particularly with elbow flexion, and may develop weakness of the intrinsic hand muscles with prolonged compression.
What is claw hand deformity and how does ulnar nerve injury cause it?
Claw hand deformity (main en griffe) occurs after ulnar nerve injury at or above the wrist. The interossei and medial lumbricals normally flex the metacarpophalangeal (MCP) joints and extend the interphalangeal (IP) joints. With ulnar nerve loss, unopposed long finger flexors cause IP joint flexion while the extensors hyperextend the MCP joints, producing a claw posture of the ring and little fingers. The index and middle fingers are less affected because their lumbricals are innervated by the median nerve.
What is the 'funny bone' sensation and what causes it?
The 'funny bone' sensation—a tingling, buzzing, or electric shock feeling radiating into the ring and little fingers—is caused by direct compression or impact to the ulnar nerve as it passes posterior to the medial epicondyle of the humerus. At this point, the nerve is superficial and relatively unprotected. Despite the common term, the sensation is caused by nerve compression, not by stimulating the humerus (the 'humorous' bone etymology notwithstanding).

Связанные структуры

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.