ulnar nerve,median nerve

 

 

After leaving the side of the neck, the ulnar nerve travels through the armpit and down the arm to the hand and fingers. As it crosses the wrist, the ulnar nerve and ulnar artery run through the tunnel known as Guyon's canal.

Guyon's Canal

This tunnel is formed by two bones (the pisiform and hamate) and the ligament that connects them. After passing through the canal, the ulnar nerve branches out to supply feeling to the little finger and half the ring finger. Branches of this nerve also supply the small muscles in the palm and the muscle that pulls the thumb toward the palm.

Tunnel Formed by Two Bones

 

The hamate bone forms one side of Guyon's canal. This bone has a small hook-shaped spur that sticks out to provide an attachment for several wrist ligaments. Known as the hook of hamate, this small bone can break off and press against the ulnar nerve within Guyon's canal.