Here are some more practice sketches. This time I'm focusing on shoulders, fingers and everything in between. The arms aren't just straight cylinders as I tend to draw them. By doing a few of these, I learned how complex the whole structure can be. I'm going to attempt to use some technical anatomical terms here. But, I could be wrong with my naming conventions as my knowledge of anatomy comes from wikipedia articles.
h4. Top Left
This one was fairly simple. The combination of a fairly flat lining and relatively relaxed pose served as a warm up, more than anything.
h4. Top Middle
In here, things get interesting. The arm is pulling something in closer and this means that more muscles are contracted and easier to identify.
The deltoid muscle gives the defining shape of the shoulder. It's round and there isn't much going on in this example
The next muscle shape on the inside of this sketch is the biceps brachii. Since the forearm is twisted towards the shoulder, the biceps are contracted and there's more shading involved, closer to the forearm.
Also, the Triceps brachii, which connects to the elbow, is also defined in the shadows.
The forearm's defining feature is the lateral antebrachial group of muscles which are much thicker than the wrist, especially since the arm is in the act of pulling.
h4. Top Right
Again, there is more definition with the deltoid. The extensor carpi ulnaris is also quite prominent on the forearm. I included a bit of the torso and, consequently, the small area where the pectoralis major connects to the humerus.
h4. Bottom Left
A bit to dark to see anything. The thing to note is that the brachio-radials really do stick out. The elbows, when the arm is extended, cause the skin to fold and compress, making the area darker than the rest. This applies to the knuckles as well. Although I did over do them in this example.
h4. Bottom Right
Most of what I said in the previous one applies here. This one was a bit better and showing structure as there was more lighting.