Why small intestine is longer than large intestine?
The small intestine needs to be longer because of the work it does. First, fluid is added into the small intestine, mixing into what we eat and drink; the small intestine then processes nutrients and separates out the waste. Nutrients get absorbed from the small intestine, while waste passes through to the large intestine. Excess fluids get pulled back out of the small intestine, to be passed through the kidneys. Some fluid remains in the bulk going into the large intestine, to keep the solid waste moist (if the remaining fluid gets removed then the person becomes constipated).