Joints

By definition, a joint is flexed when the angle between the bones is decreased. If that angle is increased, the joint is extended. Can you visualize how a muscle that crosses the caudal aspect of the shoulder joint, such as the teres major muscle, will flex the shoulder? Likewise, the supraspinatus muscle crosses over the cranial aspect and extends the shoulder.

I do not require you to learn the origins and insertions of muscles (i.e., where they attach on the bones), but it is to your advantage to dissect and find these attachments so that you can visualize the result of contraction of the muscles. REMEMBER: Muscles only shorten and pull, they do not lengthen and push. See Fig 28, pg 50 of Guide to the Dissection of the Dog for line drawings of the muscles with their attachments.