Agroup of organ systems that work together to perform a common function

Organ systems:

they work together to carry out a particular function for the organism.

Explanation:

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.