Which of these body systems has cells that attach to each other to form a leak-proof barrier? Select one:

Endocrine system.

Respiratory system.

Reproductive system.

Urinary system.

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.

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?

i think its white blood cells

i hope this