Yes, BLASTULA is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, A 1, S 1, T 1, U 1, L 1, A 1.

Is it a valid word?

BLASTULA is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs

Not playable in Scrabble US: BLASTOSPHERE.