Some stimuli act as attention-getting stimuli due to their physical characteristics; others, due to their meaningfulness, act as attention-holding stimuli.
For example, somebody's physical appearance, of a person who is attractive, is used as an attention-getting stimuli, but their psychological qualities are what hold your attention due to their meaningfulness.
Answer:
They pick up oxygen from the lungs and drop off oxygen to the cells through the capillaries
podrias ser mas especifico??