Because Thomism is a dominant expression of Catholic theology, I will answer accordingly.
Your spiritual soul is not a substance in its own right — separate from the body, as it were. Rather, it is the form of a single human substance, which is bodily and also has immaterial (spiritual) capacities. In Thomistic language, the “form” is the principle that, when paired with matter, makes an individual reality “this” and not “that.”
There is a sort of hierarchy when we identify the material constituents of a substance (individual reality, like a human). If I lost my right leg, I’d still be human. I’d still be me. I’d still have “form.” Take away all my limbs, and so it remains. Take away my heart, or lungs, or whatever, and I die: So my body no longer remains in its integrated, unified whole-ness. What was my body is no longer informed — with no unifying principle (form).
And I have to go right now, but I didn’t want to delete what I had. Maybe I’ll be able to come back later, or someone else trained in Thomistic thinking can add more.