The Self is in the heart. There are the 101 arteries, and in each of them there are a hundred (smaller veins), and for each of these branches there are 72,000. In these the Vyâna (the back-breathing) moves.

In plain words: The Self lives in the heart. From the heart spread 101 main channels, each with a hundred smaller branches, and each of those with 72,000 more. Vyana, the breath that moves all through the body, travels in these channels.