ulnar nerve medical: Nervus ulnaris
Definition
The ulnar nerve (Nervus Ulnaris) is an important arm nerve. In its course along the forearm, it is oriented to the ulna after which it was named. Like most arm nerves, it consists of fibers that transport sensitive information from the skin and joints to the spinal cord and brain (sensitive afferences) and of motor fibers that send impulses from the brain to the arm muscles (motor effects).
As one of many nerves, the ulnar nerve is composed of the brachial plexus. The spinal nerves from the cervical medulla of the spinal cord (C5-C8) join together immediately after exiting the spinal cord to form this nerve bundle, which is called the brachial plexus. All nerves supplying the arm emerge from this nerve bundle.
The nerves of the brachial plexus are called :
- Short branches: N. subscapularis, N. thoracodorsalis, Nn. pectoralis medialis and lateralis, N. cutaneus antebrachii medialis, Nn. intercostobrachiales
- Long branches: N. musculocutanes, N. axillaris, N. radialis, N. medianus, N. ulnaris
A nerve contains fibers that transport sensitive impulses from the skin and joints back to the brain (afferences) and at the same time fibers through which impulses are sent from the brain to the muscles (efferences).
The ulnar nerve runs from the axel along the inside of the upper arm to the elbow. Behind the bony prominence of the elbow (Epicondylus medialis) it moves to the front inner side of the forearm. All along the way it is hidden and protected by a muscle of the forearm (M. flexor carpi ulnaris).
Unlike its sibling nerve, the medial nerve, the ulnar nerve migrates above the carpal tunnel to the palm. The ulnar nerve (nerus ulnaris) primarily controls muscles of the hand. The most important of the supplied muscles are: Other muscles supplied by the ulnar nerve:
- Thumb puller (M. adductor pollicis): Pulling and bending of the thumb;
- Short thumb flexor (M. flexor pollicis brevis): Bending of the thumb;
- Small finger spreader (M. abductor digiti minimi): Spreading, stretching of the small finger;
- Small finger flexor (M. flexor digiti minimi): Bending of the small finger;
- Worm-shaped finger muscles (Mm.
lumbricales): Flexion of the fingers in the base joint, extension of the fingers in the end joint;
- Finger spreader (Mm. interossei): Spread the fingers.
- Short palmar muscle (M. palmaris brevis)
- Deep finger flexors (M. flexor digitorum profundus)
The feeling of the edge of the hand including the ring finger is provided by the ulnar nerve. In the palm, the area extends to the middle of the ring finger, on the back of the hand to half of the middle finger.
Injuries to the elbow can lead to nerve damage. For example, a torn ligament at the elbow can affect the ulnar nerve. If the nerve is irritated at the level of the elbow joint, it makes itself felt with a painfully vibrating gribbling sensation, which has given the bony protrusion the name of the funny bone.
Permanent pressure damage in this area leads to the image of the “claw hand“: The fingers are overstretched in the base joints, and bent in the middle and end joints. In addition, there is sensitive skin loss at the edge of the hand and ring finger. Injuries in the area of the wrist lead to such a claw hand, but the sensitivity of the edge of the hand is not affected. If, in addition to the ulnar nerve, other nerves are also damaged, a complete brachial plexus paralysis can also occur.
