section_path: Anatomy and physiology/Digestive and excretory systems/Urinary bladder
section_name: Urinary bladder
paragraph_text: Urinary bladder
  
  Most aquatic and semi-aquatic amphibians have a membranous skin which allows them to absorb water directly through it. Some semi-aquatic animals also have similarly permeable bladder membrane. As a result, they tend to have high rates of urine production to offset this high water intake, and have urine which is low in dissolved salts. The urinary bladder assists such animals to retain salts. Some aquatic amphibian such as Xenopus do not reabsorb water, to prevent excessive water influx. For land-dwelling amphibians, dehydration results in reduced urine output.
  
  The amphibian bladder is usually highly distensible and among some land-dwelling species of frogs and salamanders may account for between 20% and 50% of their total body weight. Urine flows from the kidneys through the ureters into the bladder and is periodically released from the bladder to the cloaca.