Good try. I'll do a couple and post mine. Keep up the good work.

That looks like the other head of the sternocleido-mastoid muscle. In this model it's very prominent, but it should connect about 1/3 of the way from the center of the sternum along the clavicle. When the model's neck is stretched out like that, it creates that deep depression you don't normally see. When relaxed, it makes a more flat triangular shape that is typically indicated in drawings or sculpture.

More reference photos used in the above studies

Nice work!

Hi @Jason Winter, these drawings look really nice! Very good edge work! I'll do my best to help you further: - I mentioned in a previous critique that I like to do "x-ray" drawings, where I clearly indicate muscles and bones, making sure that I understand what's beneath. I think you would get much more out of your studies if you did the same. Track everything with light lines, make sure that you understand everything. Then you can add the beatiful shading on top. I think Stan makes a good role model; He draws though, clearly tracking the muscles, yet adds some beatiful core shadows - I would familiarize myself more with the structure of the throat. In the second drawing for example, I would draw the core shadow differently to better show the form of the thyroid cartilage - In the first study In think you misinterpreted the thyroid gland for being the sternohyoideus. Refer to Stan's example. One clue that makes certain it's not the sternohyoideus is the direction. It should attatch to the sternum, note how you have them going to the clavicles. It would also be nice if you indicated the thickness of the jaw I hope this was helpful :) Keep up the good work!

Answering your questions: There won't be folds in the muscles. The folds will always happen in the skin in response to the contraction of the muscles. But the muscles themselves don't really fold. It's like when you wear a long sleeve shirt. When you bend your arm, its volume remains the same but as you bring the parts together the fabric will compress resulting in folds in the bending side. With that being said let's analyse the neck. When you extend the neck the semispinalis capitis, splenius capitis and trapezius will contract and bring your head back. Normally the result more plausible would be a straight line. But, in reality as the trapezius is attached to the spine through the nuchal ligament, so it will inherit its curvature. Since it's the muscle more close to the surface, it will force the other ones to its path and the result will be two fuller cylinders that follow more or less the curvature of the cervical portion of the spine. Depending on your body fat percentage, you can try poking the back of your neck when you look up. It's possible to feel the hard form of the muscles under the soft skin folds. That, hopefully will give you a better understanding o what happens. But remember that in reality you'll probably see the forms of the muscles blending the folds or in some cases it will be covered by long hair. But if you understand the theory you can design accordingly. Best regards