The digestive system of turtles is not much different from other typical vertebrates.
The thick and curved stomach is attached by its side to the very large liver.
The thin-walled urinary bladder discharges into the cloaca.
The nature of the produced waste depands on the environment in which a species lives.
Tortoises from dry areas excrate virtually insoluble uric acid
( C5H4O3N4 ), allowing them to save the absorbed
water in large volumes in the bladder ( like Galapagos tortoises ). The semiaquatic turtles
produce relatively nontoxic and water soluble urea ( NH2CONH2 ),
requiring some water for its elimination, while the aquatic turtles
excrate large amounts of ammonia ( NH3 ), a highly soluble and toxic substance
which needs large volumes of water in the process of its elimination.