Ulnar nerve: course behind the medial epicondyle, muscles and sensation
Where does the ulnar nerve run?
Have you ever knocked the inside of your elbow and felt a jolt run down to your little finger? That is the ulnar nerve. The spot is called the funny bone, but what you hit is the nerve, not a bone.
It arises from the medial cord of the brachial plexus, runs down the inner arm, passes behind the inner bump of the elbow, and continues along the little-finger side of the forearm to the wrist, following the ulna. Its fibres come mainly from C8 and T1, sometimes also C7; textbooks differ.
Elbow: behind the medial epicondyle
In the upper arm it runs medial to the brachial artery, then pierces the medial intermuscular septum in mid-arm and descends in front of the triceps. At the elbow it lies in a shallow groove behind the medial epicondyle; from behind, as in the view above, you can see it curve round the back of the bump. With almost no muscle between bone and skin here, a knock reaches the nerve directly.
Forearm and hand: most of the small hand muscles
It enters the forearm between the two heads of flexor carpi ulnaris and supplies that muscle and the medial half of flexor digitorum profundus. At the wrist it passes superficial to the flexor retinaculum, through the ulnar canal (Guyon's canal) beside the pisiform, rather than through the carpal tunnel like the median nerve. In the palm its deep branch supplies most of the small hand muscles.
・Motor: flexor carpi ulnaris, medial half of flexor digitorum profundus, hypothenar muscles, interossei, medial lumbricals, adductor pollicis
・Sensory: the little finger and the medial half of the ring finger, palm and back
Name and terms
Ulnar means of the ulna. Related terms: medial epicondyle, ulnar canal (Guyon's canal), cubital tunnel. The Latin is nervus ulnaris.
See it in the app
How the ulnar nerve curves behind the elbow cannot be seen in a front view. In the 3D anatomy app teamLabBody you can keep only the bones and the nerve and rotate to the back to see it pass behind the medial epicondyle, then select its palmar, dorsal and deep branches. Cross sections are available with the PREMIUM plan.
FAQ
- Where does the ulnar nerve run?
- From the medial cord of the brachial plexus down the inner arm, behind the medial epicondyle at the elbow, along the little-finger side of the forearm and through the ulnar canal into the palm.
- Why does knocking the elbow tingle down to the little finger?
- Behind the medial epicondyle the ulnar nerve lies just under the skin with almost no muscle over it, and it carries sensation from the little finger and half the ring finger.
- Which muscles does the ulnar nerve supply?
- Flexor carpi ulnaris and the medial half of flexor digitorum profundus in the forearm, and most small muscles of the hand.
Related articles
・Median nerve: runs down the middle and through the carpal tunnel
・Brachial plexus: source of the ulnar nerve
・Ulna: the forearm bone it follows
・Flexor digitorum superficialis and profundus: it supplies the medial half of the deep flexor
・Brachial artery: it runs beside it at first
