Tracing the History of Civilization to a Pair of Bumps on a Bone

The plan for a lesson is often written in the heat of the moment right before delivering it. I’m a science teacher who teaches in a high school that specializes in the creative and performing arts. This year I have four different classes, including a freshman science course that I developed only last year, Biology, AP Biology, and Anatomy and Physiology of the Human Body. There are days when prep time just runs out. All I knew was that it was Musculature of the Arm Day for the Anatomy class. Students had seen the muscles in the dissecting tray of the white rat. Today they would turn in the coloring page based on the chart of names, origins, insertions, and actions of these muscles. And today I was going to work up a quiz. As students stumbled into class, I noticed that two bone markings were listed three times each, the medial and lateral epicondyles of the humerus or upper arm bone. Aha. It occurred to me right then and there that these two places were the key to my impromptu lesson plan.

“Yes, Mr. DePrez, I see the flared end to the upper arm bone. So?”

“It’s called the humerus, remember?” I retorted.

“Oh, yea.”

“Now think about it, people. You dancers can’t do pirouettes without the solid floor underneath your feet. The Olympic figure skaters this week can’t do those fancy axel jumps without leverage. They need the ice to launch those spin jumps, don’t they? In other words, dancers and skaters need a foundation against which to push off.”

“Yeah, yeah,” came a response from the back of the room.

“Now consider flexion and extension of the wrist and fingers. If you’re going to curl these bones and bring them back to their original position, don’t you need a similar launching pad? Look down the list of muscle origins where the forearm muscles are anchored by their tendons. How many times do you see epicondyle of the humerus? Lisa, read them for us, please.”

“Origin of the flexor carpi ulnaris: the medial epicondyle of the humerus. Origin of the flexor carpi radialis: the medial epicondyle of the humerus. Origin of the flexor digitorum: the medial epicondyle of the humerus. Origin of the extensor carpi ulnaris: the lateral epicondyle of the humerus. Origin of the extensor carpi radialis: the lateral epicondyle of the humerus. Origin of the extensor digitorum: the lateral epicondyle of the humerus.”

“Well! Just one pair of sites provides the origins for the muscles that work the hands, huh? Humans are tool makers. Ever since the Neolithic Revolution, during which they domesticated plants and animals for a steady food source, humans have grasped and manipulated their world with their hands. The one anatomical feature that provides the foundation for grasping and manipulating, and thus has enabled our fine minds to work their magic in making things with tools, is a pair of epicondyles on the humerus. The means of empire-building boils down to a pair of bumps on a bone. Now what I want you to do is pull out a sheet of paper, number it one to six for listing the six flexion and extension muscles of the wrists and fingers, and, oh, skip a space so I can ask you what bone markings provide the leverage for these actions.”

Not one student failed to state every time the epicondyles of the humerus.