I was actually tracking along with what you were saying until you shifted over to human anatomy as what is meant by "inside you" in scripture. That was an unexpected left turn off the road into the cornfields.
In my understanding of the esoteric nature of the Christian faith, the "inside" of us, the "interior spaces", is not referencing the stuff underneath the skin: bones, tendons, internal organs (skin is an external organ), heart, liver, and such. Those too, are all "external" to us. They are not what is "inside" us in the context of a spiritual reference.
The interiors of us, is consciousness. It is what is in and behind our thoughts and motivations, our desires, the core of our self identities, and beyond the form in this human body. It is the human soul, to give some term for it. Making clean the inside of the cup, clears the way for the kingdom of God to arise within us, and from us flow out to the world. It means, making your soul open to God. It doesn't mean your rib cage.