How the water level in the body is controlled – osmoregulation
By Manaahil Faheem

Maintenance by an organism of an internal balance between water and dissolved materials regardless of environmental conditions our tissues do not lose or gain water by osmosis. In many marine organisms osmosis (the passage of solvent through a semi permeable membrane) occurs without any need for regulatory mechanisms because the cells have the same osmotic pressure as the sea. The osmotic strength of our blood obviously depends upon how much glucose and mineral salts it contains as well as how much water is present other organisms, however, must actively take on, conserve, or excrete water or salts in order to maintain their internal water-mineral content.

more water
urinate more
diluted urine
blood becomes diluted
less water
urinate less
concentrated urine
blood becomes more concentrated

The body needs a constant amount of water in the cells. Our bodies take in water from whatever food and drinks we have. We even get some water when we respire by burning glucose to release energy.
We lose water in sweat, faeces, urine and when we breathe out (on a cold day you can see this water as it condenses into vapour).

(BBC,2008) Cold or hot temprature"

For the cells of our body to work properly, it is important that their water content is maintained at the correct level. This means our body must maintain a balance between the water we take in and the water we lose. This is done by the kidneys.


Nigel D Purchon. (19 November 2006). Osmoregulation. Available: http://www.purchon.com/biology/osmoregulation.htm. Last accessed 13 April 2009.

"osmoregulation." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online. 12 April 2009 <http://www.britannica.com/EBchecked/topic/434048/osmoregulation> Last accessed 13 April 2009.

Grath Williams. (2006). Homeotasis. In: Stanley Thrones Biology for You. 2nd ed. United Kingdom: Nelson Thrones Ltd. p110, 113

BBC, 2008 " Homeostasis" [Internet].
Available from: http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/homeo/homeostasis5.shtml[Accessed date April 13th]