Complex sentence: Villi serve the same purpose as the alveoli in the lungs: both increase surface area, which helps to increase the transfer rate of nutrients into the blood through diffusion, although alveoli also transfer wastes out.
Split into simpler sentences: Villi serve the same purpose as the alveoli in the lungs. Both increase surface area, which helps to increase the transfer rate of nutrients into the blood through diffusion, although alveoli also transfer wastes out.