Question

Whats homeostasis???

thanks :)

Answer 1

Homeostasis is an state of equilibrium, in which all body systems are working and interacting in an appropriate way to fulfill all the needs of the person and/or the body.

Answer 2

but i have to link it to the kidneys :S

Answer 3

So think about what the kidneys do. What kind of equilibrium are they keeping?

Answer 4

Remember that the kidney filters blood and produces urine. The kidney has a a cortex and medulla which both have closely controlled ion concentrations. The parenchyma of the kidney, the nephrons, make use of these and produce concentration gradients.

Most animals can only produce a dilute urine (frogs for example) or a very concentrated urine (kangaroo mouse for example). Humans can produce both, with a urine osmolarity range of about 90-1200 mOsm. This is accomplished mainly by selectively opening and closing ion channels (sodium, potassium, HCO3) and water channels (aquaporins) in the distal convoluted tubule. The other parts of the nephron (the loop of henly especially) are also important to this process. It is important to note that the kidneys also play a role in maintaining blood pressure by controlling the osmolarity of your blood. if your blood is too dilute, the kidneys conserve more salts. If your blood is too concentrated, your kidneys conserve water. Water is always conserved at the expense of salts, and salts at the expense of water and another salt.

Basically, your kidneys are important for maintaining homeostasis in the salt concentrations in your blood. Thats pretty important.

Kidneys are complex, but i hope this helped. I am going to stop here since i probably need to look stuff up to be sure of anything more specific. Look around, there is lots of info on them:
http://en.wikipedia.org/wiki/Nephron