Changes

==Introduction==

|backcolour = C1F0F6

|linkpage =Urinary System - Anatomy & Physiology

|linktext =URINARY SYSTEM

|maplink = Urinary System (Content Map) - Anatomy & Physiology

 

This section is devoted specifically to the renal anatomy and physiology of fish, aquatic and terrestrial amphibians, birds and reptiles. These animals excrete nitrogenous waste differently to domestic mammals, this combined with the very different habitats where these animals exist results in a variety of different renal mechanisms and appearances.  

This section is devoted specifically to the renal anatomy and physiology of fish, aquatic and terrestrial amphibians, birds and reptiles. These animals excrete nitrogenous waste differently to domestic mammals, this combined with the very different habitats where these animals exist results in a variety of different renal mechanisms and appearances.  

=====Saltwater=====

=====Saltwater=====

The environment is hypotonic compared to the body of the fish therefore water is lost across their gills so they drink sea water to replace this which results in a large intake of salt (activates Angiotensin 2).  They excrete both ammonia and NaCl across their gills and further NaCl across their skin.  Their kidneys have small or absent glomeruli and their main function is the elimination of excess divalent ions e.g. Mg²⁺

The environment is hypertonic compared to the body of the fish therefore water is lost across their gills so they drink sea water to replace this which results in a large intake of salt (activates Angiotensin 2).  They excrete both ammonia and NaCl across their gills and further NaCl across their skin.  Their kidneys have small or absent glomeruli and their main function is the elimination of excess divalent ions e.g. Mg²⁺

==Amphibian==

==Amphibian==

==Avian==

==Avian==

 

====Anatomy====

====Anatomy====

====Avian Renal Portal System====

====Avian Renal Portal System====

 

In birds the blood from the hindlimbs is carried directly to the kidneys.  It bypasses the glomeruli and waste products in the blood are secreted directly into the tubules.  This is thought to be a more efficent way to excrete uric acid and urate.  It is of significance when injecting these animals if the injection is given in the caudal half of the body most of the drug will be potentially lost in the urine before it has time to act it may also be toxic to the kidney as it has not been metabolised by the liver

In birds the blood from the hindlimbs is carried directly to the kidneys.  The cranial and caudal renal portal veins deliver blood from the hindlimbs into the capillary beds of the interlobar arteries.  Therefore blood which has already been through capillary beds in the hind limbs mixes with blood directly from the heart.  It bypasses the glomeruli and waste products in the blood are secreted directly into the tubules.  This is thought to be a more efficent way to excrete uric acid and urate.  A portal valve regulates how much blood from the hindlimbs passes through the kidneys.  When open very little blood enters the capillary beds as it follows the path of least resistance.  If the valve narrows then blood is forced into the capillary beds.  However some blood always escapes thanks to connections with both the caudal mesenteric veins and vertebral sinuses. It is of significance when injecting these animals if the injection is given in the caudal half of the body most of the drug will be potentially lost in the urine before it has time to act it may also be toxic to the kidney as it has not been metabolised by the liver

====Other Roles of the Avian Kidney====

====Other Roles of the Avian Kidney====

* Sea turtles have modified tear glands which allow them to secrete salt from their eyes

* Sea turtles have modified tear glands which allow them to secrete salt from their eyes

====Other Roles of the Reptilian Kidney====

==== Other Roles of the Reptilian Kidney ====

* Activates vitamin D

*Activates vitamin D  

* Synthesises Vitamin C

*Synthesises Vitamin C