Answer:
a) blood from the heart flows through your capillaries and collects oxygen from the alveoli. while that happens, co² passes out of the capillaries and into the alveoli. when you breathe out, you get rid of co² and oxygen is returned to the heart and pumped out to the body.
b) digested nutrients are absorbed into the bloodstream through capillaries in the villi that line the small intestine.
