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Hi @Macario Lopez, nice study! - Maybe you could give the bottom of the palm a more rounded shape to emphasize that it's an ellipsoid joint, instead of drawing a box. - Some of the ellipses on the cylindrical forms are a little off. But you got it really nice on the inner lower end of the humerus. So maybe you know how to construct a cylinder already? Maybe it's just a matter of getting more experience doing it, trying some more difficult angles. If you're up to it, fill a page with cylinders from different angles. Remember to draw through. Feel free to tag me (@Jesper Axelsson) if you want me to take a look. - The circle for the sphere of the head of the humerus, isn't really circular. Maybe practicing drawing circles, and checking with a compass could be a good idea. The crosscontours are also a little off, so maybe do the same as with the cylinders; fill a page with spheres from different angles. Try to make it feel like the crosscontours are 90 degrees to one another (representing the x, y and z axis). Maybe you could use this 3D model as reference https://sketchfab.com/3d-models/lined-sphere-aa19bbaf6db94bfd93a40af6c0413d08. - A tip when drawing the crosscountors when drawing from reference, such as this image of the skeleton of the arm: Imagine touching the forms as if you had a sculpture in front of you. Imagine wrapping your hand around the humerus for example, to make sure that you know what direction it has. Your hand will wrap around like the crosscontour line would. I hope this helps :)

I think the point is to get to know and understand the joints. So you do what you have to get there. Maybe start by drawing with the same perspective as in the image, then try drawing it in other positions or angles. I think Marshall's example videos will give you a good idea of how to approach the assignment. I hope this answers your question :)