Changes

==Amphibian==

==Amphibian==

===Anatomy===

====Anatomy====

In amphibians urine moves from the kidney down the ducts into the cloaca and then onto a urinary bladder.  Caudates and Anurans posses renal portal veins which carry blood from the hind limbs to the kidney before it goes back to the heart.  They have paired posterior kidneys which lie retroperitoneally.  Caecilians have no renal portal veins and have one kidney the full length of the coelom

In amphibians urine moves from the kidney down the ducts into the cloaca and then onto a urinary bladder.  Caudates and Anurans posses renal portal veins which carry blood from the hind limbs to the kidney before it goes back to the heart.  They have paired posterior kidneys which lie retroperitoneally.  Caecilians have no renal portal veins and have one kidney the full length of the coelom

===Physiology===

====Physiology====

* Aquatic amphibians excrete ammonia whereas terrestrial species excrete uric acid

* Aquatic amphibians excrete ammonia whereas terrestrial species excrete uric acid

* They have a urinary bladder

* They have a urinary bladder

====Aquatic Amphibians====

=====Aquatic Amphibians=====

Aquatic amphibians have extremely water permeable skin and therefore lots of osmosis occurs across the skin.  It falls to the kidney to excrete excess water and ammonia

Aquatic amphibians have extremely water permeable skin and therefore lots of osmosis occurs across the skin.  It falls to the kidney to excrete excess water and ammonia

====Terrestrial Amphibians====

=====Terrestrial Amphibians=====

Terrestrial amphibians have the totally opposite problem to their aquatic counterparts.  To them water conservation is very important as water is lost via various routes including evaporation.  They therefore have a urinary bladder which is permeable and water is reabsorbed across it this is controlled by arginine vasotocin (AVT).  This chemical increases the number of aquaporins in the membrane.  They excrete urea and are able to decrease their GFR if water is reduced.

Terrestrial amphibians have the totally opposite problem to their aquatic counterparts.  To them water conservation is very important as water is lost via various routes including evaporation.  They therefore have a urinary bladder which is permeable and water is reabsorbed across it this is controlled by arginine vasotocin (AVT).  This chemical increases the number of aquaporins in the membrane.  They excrete urea and are able to decrease their GFR if water is reduced.