I invented the term internal sacrificial biologically bound metabolic support in an attempt to describe the exact nature of the very specific fixed connection of a umbilical cord. Adjust the terminology to your liking, but anything short of a direct analog of a fixed, biological structure connecting the two persons in a host/dependent situation in which an act of agency would be necessary to sever it won’t be useful for the point of argument. I don’t know of any useful analog so this is why I think arguments around abortion should be had on their own terms without trying to draw on analogies.