Why don't human cells have cell walls

Because Human Cell's cell membrane does the Cell Wall's job as well as determine what goes in and what come out. Unlike the animal cell, the Plant Cell's cell membrane can only do one job at a time, so it has the Cell wall to do the job of keeping the cells shape and structure.

I’m not exactly sure what your trying to ask, but if it’s how an organelle is similar to a body system or a part a nucleus is like a in function. but i don’t fully understand what you’re trying to ask