Problem:
With the osmolarity of the average vertebrate being around 300mOsml, and salt water having an osmolarity of 1000mOsml,
Question: Why does the water from the shark not leave to the salt water around it?
I presume the scales must act as a barrier to stop water form leaving, but with the blood vessels being exposed to the saline water in the gills, why does water not leave the body?