Hi everyone!

 

Great to be here, this being my first post I'll just briefly introduce myself - I'm a final-trimester Health Sciences/Arts student from Australia, and have recently started a unit on anatomy just as an elective to finish things off (my main areas are nutrition and health promotion).

 

Now onto my question, here and there I see references to 'functional' and 'accessory' motions/actions. I have a vague idea that the latter term implies something auxillary to a main feature, but I am not sure exactly how to use the terms in an anatomical context.

 

For example, in regards to articulations, what exactly (if any) would be 'functional' and 'accessory' motions of the glenohumeral joint, and in regards to muscles, what would be 'functional' and 'accessory' actions of the gluteus maximus?

 

Thanks for your help!

It's more on a continuum. A given muscle or joint may primarily function in one direction, but be capable of other actions, especially when other muscles stabilize the joint.

 

A good example of it is your biceps. Because it inserts onto your radius, it can function both as an elbow flexor *and* as a supinator, rotating the forearm. It's not really appropriate to call either one "primary" unless there's a good anatomical reason, such as a major difference in the moment-arm about the joint. An example of that would be the gastrocnemius, which has a powerful ankle-extensor function, but a weak knee-flexor function due to the positions of the muscle attachments (long lever arm at the ankle, short lever arm at the knee).

Alright, thanks man.