Urogenital opening

The urogenital opening is where waste products of the body and reproductive fluids are expelled to the environment outside of the body cavity. In some lower organisms, including birds and many fishes, discharge from the urological, digestive, and reproductive systems empty into a common sac called the cloaca. In more advanced organisms, these three systems are more separated. In the human female, separate orifices have evolved for all three, while in the male, a common "urogenital orifice" discharges both urinary and reproductive fluids from the urethra. Essentially birds rub their holes together when mating.