According to Brahmanda purana, brahma commensed creation in this following chronological order [Bh Purana - Quote 25 - 50].
Prākrta Creations (pertaining to Prakruti)
- Mahat -- Great Principle
- Tanmatras -- Subtle Elements
- Vaikārika -- Creation pertaining to Sense organs
Vaikrta -Mediated creations
- Mukhya Sarga -- Insentients or immobiles
- Tiryak srota [Beings whose digestive fluids flows obliquely] -- Animals and lower creatures.
- Ūrddhva Srotas [Beings whose digestive fluids flows upwards] -- Devas, Gandharvas etc
- Arvāksrotas [Beings whose digestive fluids flows Downwards] -- Human beings
Mind born sons of brahmas are classified separately.
Devas are repeatedly mentioned in various scriptures that they are free from death (till manvantara), hunger and diseases. Also in vedas they quote that, Indra and other devatas drink copious amount of somarasa. All picturization of devas looks to be having humane form in divine bodies.
My Question is, why does devas are classified as Ūrddhva Srotas?
Intensive googling didn't help me out on this aspect.