Lookin' great there Joseph.
some quick crits for ya:
the abs seem quite saggy, and are a bit lower than where they should be. The top row of your six pack there is quite elongated. Also your head is a tad fat - i'd slim it horizontally by a couple of pixels. I notice that you put an eye guideline on your head there. -just a heads up, the eyes are generally placed in the center of the head. Yours is a bit below halfway, but it could be because your trying to give the effect of him looking down. the wrist and hand area is quite week right now, you may want to look up some references there.
set aside all of the technical issues, this is quite a solid piece, Joseph. The one and most important I can give you is this: Right now, it is nothing more than a template or guide of some sort. I can't say much for the actual art of it right now. It's a front view line-art of some naked guy with no dick and no face with some AA. The *real* work comes when you apply this new learning of anatomy into various situations and compositions. Try applying this to different poses, characters, lighting conditions, etc. You seem to have done a fine job at knowing the placement of the muscles, now apply it.
great work there Joseph,
-Dan
