Medical Mysteries, She Wrote

Have you ever wondered why it hurts when you hit your funny bone? Or why your eyes close when you sneeze? WebMD has the answers to these and other perpetually perplexing medical mysteries.

By Heather Hatfield
WebMD Feature

Reviewed by Louise Chang, MD

Why is hitting your funny bone anything but funny? Does sneezing really make your eyes pop out of your head? And why, no matter how hard you try, can't you stop from yawning when the person next to you yawns? Here are some of life's little medical mysteries -- solved.

Hitting Your Funny Bone

The funny thing is, the funny bone isn't a bone at all, but a nerve, and hitting it is anything but funny -- in fact, it's painful.

The nerve that is referred to as the funny bone is the ulnar nerve, which extends down the arm, across the elbow, and into the hand. It provides sensation to the little and ring fingers and activates many of the muscles in the hand, according to the American Association of Orthopaedic Surgeons web site.

"The ulnar nerve happens to be very superficially placed in the back of your elbow," says Ed Toriello, MD, a fellow of the American Academy of Orthopaedic Surgeons. "At this spot, it lies directly under the skin and runs in a hard, bony groove on its way to your hand."

Why is hitting it guaranteed to make you cringe with pain, rather than laugh, as its nickname suggests?

"Nerves are very temperamental and sensitive structures," says Toriello, who is an orthopaedic surgeon in private practice in New York. "For this reason, nerves generally course deep in muscles, where they are protected from direct contact with the things we bump into during our normal course of living. The ulnar nerve at the elbow is an exception, because it lies in a spot that is very vulnerable and protected only by a thin layer of skin."

When you bump the back of your elbow directly over the ulnar nerve, it's caught between what you hit and the bony groove, explains Toriello. A painful electrical impulse is discharged from the nerve, which runs through the arm and into the little and ring fingers.

So shouldn't it be called the painful nerve, instead of the funny bone? One theory is that the name funny bone is a pun on the Latin word humerus, which describes the part of the arm between the shoulder and the elbow, according to the Indiana University School of Medicine web site, Sound Medicine.

Another theory is that the "funny" in funny bone means strange rather than ha-ha.

"My suspicion is that the first person who experienced this sensation when he or she struck their elbow did not find it fun, but rather found it an odd sensation since it didn't seem to happen when they bumped other parts of their body," says Toriello. "So I think 'funny' in this context really means 'odd or 'strange.'"

Mystery solved.

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