Really, everything in your body plays an important role.
The least important system in the body is arguably the scalp hair. It only serves as a means to look good and to attract the other sex.
thighs
Isn't there just one organ system(in each body :p) ? O.o
respitory system
The reproductive system is used to produce children.
it is used in the satr
Immune system!
Food.
Circulatory system
The cardiovascular system.
no
The integumentary system is used as a waterproof barrier that blocks the entrance of pathogens into and prevents water loss from the body.