The anus has three main functions. (1) releases waste gas in human body, that is, excrement. (2) The excretion of waste in human body is displacement. (3) Gate control function: prevent intestinal contents from involuntarily overflowing out of the body, and prevent foreign bodies such as gas and liquid from entering the intestinal cavity.
Therefore, the anus will not absorb nutrients and water, nutrients must be absorbed in ionic state, while the anus and intestine will absorb water in feces.