A question that routinely is asked is "which muscle does this work?" The question that I have is "what value do you receive knowing the answer?" What purpose for you, as the exerciser, does knowing which muscle is the one being used?
Part of my undergraduate and graduate studies consisted of anatomy, physiology, and biomechanics. Each of these allow for me to understand which muscles are being used, which energy systems are dominant, agonist/antagonist movement, and a variety of other fairly important items when it comes to understanding how the body responds to exercise. So for me to answer that question to myself or better yet, why am I working this muscle, is much more relevant than what muscle is it.
The specific muscle being worked isn't hugely important unless your bodybuilding or in therapy. For many, it's the bio-energetic system(s), the energy systems the body uses, which is usually more relevant. The amount of muscle recruited to perform a task is also generally more relevant to me than which muscle I'm working.
Now, don't get me wrong, if I tell you that you're working your "lats" while performing a pull-up I'm not lying, they're being used. But, what does this tell you? It honestly doesn't fully help me unless I'm trying to hypertrophy (grow) or recruit (contract) the lats. And even still, lats isn't really the name, it's shortened for lattissimus dorsi. It is however, one of the primary movers in a pull-up. It helps to stabilize the spine and the upper body in general. Generally speaking, it's involved in all large compound movements such as dead-lifts, squats, and bench press.
So knowing which muscle being worked, has it helped you with this knowledge? Or is it important to ask "why am I working this muscle?" Think of questions like that as opposed to which muscle, which really doesn't serve a practical matter.
