Your statement "Because the flesh out of which we are made is intrinsic" begs the question "Did Jesus share flesh with Mary, or was Mary a vessel to carry the child from the Holy Spirit?"
Now I'm just getting silly, but "How did Mary become pregnant?" Did the Holy Spirit create a whole viable life within Mary or did the Holy Spirit fertilize one of her eggs.
The prophesy in Isaiah 7:14 states that a virgin will become pregnant and have a son. Either scenerio fills the prophesy. Why put additional restrictions on God?
I don't think we can know. And because we can not know, how can not say that Jesus shared flesh with Mary. Because if the Holy Spirit created a whole viable life, then Mary was extrinsic, just like the sinful world.
Yes, Jesus received flesh from Mary. How do we know that? Because, for example, Christ was the Son of David, and Mary was of the house of David. If you read Anselm, for example, you see that the human race is organically connected. All were in Adam, (though not as individuals, of course). In order to save the human race, it would not have been enough for Christ to be made [de novo] a human being, and then live perfectly, and then die on the cross. Christ had to be a member of the human race, descended from Adam. In order to save Adam's race, Christ had to be from Adam. If Christ's human body had been made directly from dust, He could not have been saved Adam's race, for He would not have been one of us. He had to be one of us, in order to save us.
-A8