<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (June 2011) (Learn how and when to remove this template message) </Td> </Tr> <Table> <Tr> <Th_colspan="2"> Nephron </Th> </Tr> <Tr> <Td_colspan="2"> Diagram (left) of a long juxtamedullary nephron and (right) of a short cortical nephron . </Td> </Tr> <Tr> <Th_colspan="2"> Details </Th> </Tr> <Tr> <Th> Precursor </Th> <Td> Metanephric blastema (intermediate mesoderm) </Td> </Tr> <Tr> <Th> System </Th> <Td> Urinary system </Td> </Tr> <Tr> <Th_colspan="2"> Identifiers </Th> </Tr> <Tr> <Th> Latin </Th> <Td> Nephroneum </Td> </Tr> <Tr> <Th> MeSH </Th> <Td> Nephrons </Td> </Tr> <Tr> <Th> FMA </Th> <Td> 17640 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Nephron </Th> </Tr> <Tr> <Td_colspan="2"> Diagram (left) of a long juxtamedullary nephron and (right) of a short cortical nephron . </Td> </Tr>

Which of the following substances is not secreted by the tubules of a nephron