A lack of exercise could
a. cause bones to become longer.
b. result in porous and weak bones.
c. cause bones to lose their medullary cavity.
d. cause bones to become thicker.
e. cause bones to store more calcium.

How is the structure of our circulatory system and respiratory system related to the function of both these systems?

Pam currently runs on a track an hour a day, three days a week. how can she increase the intensity of her runs? start running five days a week start running in hilly areas or trails switch to walking six miles each day add 20 minutes to each run

True or false. mucous membranes secrete mucus that traps pathogens.