What are clouds of dust and gas from which a star first forms. they are pulled together by gravity into a spinning disc. the center of the disc becomes a star while the rest can be come a system of planets

The Nebula would be your answer, it is a cloud of dust and gas in outer space :)

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.