I went more for the flexing arm this time. Damn! It's not easy to REALLY understand how the whole thing works, but it's still pleasant to draw, and finding here & there the parts you know by heart, and how it's supposed to do here!
Oh and I can show more veins on the far right sketch, it's complex to do so cause veins are not always visible.
The part I love to draw most is the hand. Oddly, cause it's also super hard. But let me tell you this: EVERYTHING is super hard in anatomy! XD