What would it be to layer things, one on top of the other? Is there a --pose word that shows vertical positioning?

How about superimpose?

"Juxta-" means "next to," I think. In the kidney there is the "juxtaglomerular apparatus" which helps regulate the blood pressure, and it's right next to the glomerulus.


Edit: Oh well. Six minutes late. At least I can still qualify with juxtaglomerular.