other organs of the body get into that space
There is nothing that fills the space between neutrons and electrons. There may be a couple of other particles, but they do not come close to filling the space.
Volume
Air.
Not all occupies space, because air does not take space.
Gas diffuses in space.
That is called the volume.
Gallbladder is situated in liver , which fills the space .
Empty space.
It is its volume
cytoplasm
The stroma
Nothing: a vacuum is the lack of matter.