If the soul enters at conception, then where does it reside?

This kind of jumped into my head as I was driving to the library this morning.

If the soul enters the body at conception (that is, we’ll be presupposing this is fact for the purposes of this mental trip) does the soul change location during development, and at what time?

That is, does the placenta, which is a genetic twin to the foetus, and made from cells which split from the original cell, have a soul, or a “part” of the original soul? Is the soul somehow damaged upon the foetus being separated from the placenta after birth?
Do identical twins, who are genetically identical and conceived with the same single fertilised egg, share a soul?

In a post-birth human:
Is the soul damaged upon amputation of a limb?
If an organ is transplanted, does the person lose “part” of their soul, or gain part of someone else’s?
How much of the body would have to be replaced in order to affect the “stability” of the soul?
Where does the soul reside? The brain?
If a person is brain damaged, do they retain their “soul”, or can the soul also be damaged?

What, in the first place, would “move” a soul from the entirety of the human body (the single fertilised egg) to once single area (such as the brain or heart), so that an amputation or transplantation would no longer affect it?

Yes, this is what I think about while driving.