According to the Kabbalistic classic Sefer Yetzirah (Book of Creation), the 10 Sefirot represent the six directions of three-dimensional Space (south, north, east, west, up, down); the two directions of Time (past and future); and the two directions of Soul (good and evil). 6 + 2 + 2 = 10

The Axis (Teli) - the 'line' (1) that the universe revolves upon - is King in the World (Olam - Space). The Cycle (Galgal) is King in the Year (Shana - Time), as Judaism sees time as 'circular' (0).

And the Heart (Lev) is the King in the Body (Nefesh - Soul) because of its central location, and because it provides blood to all the limbs via the veins and arteries that branch out in fractal patterns like the one seen here (from 2, to 4, to 8, to 16, to 32). The gematria (number value) of Lev is 32.