Ulnar Nerve Origin and Classification
The ulnar nerve is a major peripheral nerve of the upper limb derived from the medial cord of the brachial plexus, containing fibers from spinal roots C8 and T1. It functions as both a sensory and motor nerve, with distinct distributions throughout the forearm and hand.
Motor and Sensory Functions
The ulnar nerve innervates most intrinsic hand muscles except the thenar muscles and two lateral lumbricals, which receive median nerve innervation. In the forearm, it supplies the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus, while providing sensation to the anterior and posterior surfaces of the medial one-and-a-half fingers.
Course Through the Upper Arm
After arising from the brachial plexus, the ulnar nerve descends the medial side of the upper arm, initially lying medial to the axillary artery. At mid-arm level, it penetrates the medial intermuscular septum to enter the posterior compartment, where it lies anterior to the medial head of the triceps brachii.
Passage at the Elbow
The ulnar nerve passes posterior to the medial epicondyle to enter the forearm, piercing the two heads of the flexor carpi ulnaris muscle. At this location behind the medial epicondyle, the nerve is readily palpable and particularly vulnerable to injury.
Forearm Branch Distribution
Within the forearm, the ulnar nerve gives rise to three branches: muscular branches proximally that innervate the flexor carpi ulnaris and medial half of flexor digitorum profundus, a palmocutaneous branch that supplies the medial palmar skin, and a dorsal cutaneous branch that innervates the dorsal medial aspect of the hand.
Course at the Wrist and Hand Entry
The ulnar nerve travels superficially across the flexor retinaculum at the wrist before entering the hand through the ulnar canal (Guyon's canal). It terminates by dividing into superficial and deep branches immediately distal to the pisiform bone.
Deep Branch Motor Function
The deep branch of the ulnar nerve is primarily motor in function and innervates the majority of intrinsic hand muscles. These include the hypothenar muscles, medial two lumbricals, adductor pollicis, and the interossei muscles of the hand.
Superficial Branch Sensory Function
The superficial branch of the ulnar nerve is primarily sensory and provides innervation to the palmar surface of the medial one-and-a-half fingers. This sensory distribution encompasses the corresponding medial aspect of the palm.
Ulnar Nerve | 3D Anatomy Tutorial
Key Takeaways
- •Ulnar Nerve Origin and Classification
- •Motor and Sensory Functions
- •Course Through the Upper Arm
- •Passage at the Elbow
Anatomy of the ulnar nerve. Check out the 3D app at http://AnatomyLearning.com. More videos available on http://AnatomyZone.com. This video is a collaboration between AnatomyZone and TeachMeAnatomy. For more information/material on this topic check out the article at http://teachmeanatomy.info/upper-limb/nerves/the-ulnar-nerve/ -------------------- Join the Facebook page for updates: http://www.facebook.com/anatomyzone Follow me on twitter: http://www.twitter.com/anatomyzone Subscribe to the channel for more videos and updates: http://www.youtube.com/subscription_center?add_user=theanatomyzone
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The deep branch of the ulnar nerve is primarily motor in function and innervates the majority of intrinsic hand muscles. These include the hypothenar muscles, medial two lumbricals, adductor pollicis, and the interossei muscles of the hand.
