excretoryproductsinanjmalsandotherverteb.ppt

Animal physiology it includes description of excretory system in animals
How animals excrete wastes from thier bodies
Comparative analysis of excretory system in different animals from invertebrates to vertebrates

1. UREA EXCRETING ANIMALS Nitrogenous wastes in the body tend to form toxic ammonia, which must be excreted. Mammals such as humans excrete urea, while birds, reptiles, and some terrestrial invertebrates produce uric acid as waste

2. Uricothelic organisms tend to excrete uric acid waste in the form of a white paste or powder. U reotelic animals that secrete primarily nitrogenous waste material

3. Mammals, including humans, are the primary producers of urea. Because they secrete urea as the primary nitrogenous waste product, they are called ureotelic animals. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals. It is the main nitrogen-containing substance in the urine of mammals.

4. IN OTHER AMIMALS Apart from mammals, urea is also found in the urine of amphibians, as well as some fish. Interestingly, tadpoles excrete ammonia, but shift to urea production during metamorphosis.

5. Uric Acid In birds and reptiles, uric acid is the major end-product of protein metabolism. It is produced by the liver and excreted by kidney tubules; impaired elimination is an indication of renal disease

6. Approximately 90% of uric acid is secreted by the proximal tubules in avian species. Excreted UA passes through the cloaca and is retropulsed back into the rectum and cecum, where is it broken down by bacteria and is reabsorbed. At least 60% of renal function must be lost for an elevation in uric acid to be seen; therefore, it is not a sensitive indicator of renal disease

7. SIGNIFICANCE OF URIC ACID Uric acid and guanine have an advantage of carrying away four nitrogenous atom per molecule. The nitrogen atom in uric acid arise from breakdown of the glycine ,aspartate and glutamine. Because these animals lack uricase ,they cannot breakdown uric acid.

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