Some observations: the tendons of each finger is usually evident in the back of the hand even under the skin - some people confuse them with nerves but they're actually tendons; as you may know already, the finger joints are also very evident (don't forget the thumb joints that appear on the side of the hand as you can see in the 2º drawing).
Head and neck study
And don't we all? But sadly it's a necessary evil
I'm glad you find it helpful