The four parts of the daily service follow this order. The first three thus rectify the lower three universes. The sacrificial reading (Korbanos) thus pertain to the physical world, the Biblical Praises (Pesukey Dezimrah) to the world of angels, and the Sh'ma and its blessings to the world of the Throne. This is followed by the Amidah, which pertains to the Universe of G-dly Essence, transmitting the Influences of this world according to their various aspects.
The amidah is followed by three other prayers, which transmit a continuity of G-d's sustenance to the [three] worlds , one after the other. These are the Kedushah of the Order [in U'Va letzion], the Levites'Psalm [for each day], the "None is like Our G-d" [Ain Kelokeinu]. We conclude the service with Aleinu, which speaks of G-d's kKingdom, and thus establishes His rule over all creation again after every part of it is blessed by G-d.

- From The Way of G-d, R. Moshe Chaim Luzzato, pg 307