How do sesamoid bones function as pulleys in our body?

941 views

Hi everyone! I couldnt find anything that answered this question, so here goes: Im doing osteology right now and I came across this phrase on Wikipedia:

>
“Sesamoids act like pulleys, providing a smooth surface for tendons to slide over, increasing the tendon’s ability to transmit muscular forces.”

I think I kind of understand how pulleys work: You use less force over a longer distance, yet the amount of work is the same.

Im confused as to how this is applied on sesamoid bones. I understood they are “simply” embedded into our tendons. How exactly would they be creating a larger distance, as seen by the mechanism of pulleys? And how would that put less strain on the tendons?

​

If I got it wrong please let me know! (Will flair this under physics since I believe my problem is understanding its biomechanics.) Thank you so much in advance!

In: Physics

4 Answers

Anonymous 0 Comments

They aren’t providing mechanical advantage. They are simply allowing force from one direction, to be applied with minimal loss, to another direction. If the tendons were wrapped around a bone or something ( doesn’t exist in the human body to my knowledge) then possibly it could provide a mechanical advantage.

Say you were sitting down, and want to stand up. Your patella for example, the largest sesamoid bone, will translate the force of contraction of your quads, x direction, to your tibia, y direction.

Bam, a pulley which allows you to change the direction of a force, without providing a mechanical advantage. Movement is 1:1

You are viewing 1 out of 4 answers, click here to view all answers.