kidney machine

when the kidney filtrate is produced at the glomerulus, that is filtration using positive pressure.

then, useful solutes and extra water that gets filtered out regardless of the body's condition has to go back to the blood, if not the person will produce too much urine and then die. one example would be the reabsorption of water at the collecting duct: water re-enters the interstitial space and then the blood because of the higher concentrations of salt deeper into the medulla of the kidney (which higher salt concentration is set up by the loop of Henle). the movement of water from the collecting duct's lumen to the epithelial cells and then the interstitial space is based on osmosis: the movement of solvents from a region of lower solute concentration to a higher solute concentration through a semi-permeable menbrane.

2008-03-18 12:07:05 補充：
oh sorry hmms now i know what you mean (i thought your `machine` thing is referring to the kidney itself as some sort of an analogy). we call it the `dialysis machine`... oh well :P

2008-03-18 12:07:40 補充：
okay, so if that is the case, the function of the dialysis machine is to get rid of excess solutes and water in the blood to restore homeostatsis right. i am not sure what the dislysis fluid is made of,

2008-03-18 12:07:55 補充：
but it sure does work such that it has a low concentration of solutes (e.g. sodium) that allow for excess solutes to leave the blood by diffusion through the membrane, and also, it keeps a high

2008-03-18 12:08:02 補充：
osmotic pressure using solutes undiffusible through the membrane (e.g. proteins) - thus water can exit the blood via osmosis too.

2008-03-18 12:08:07 補充：
i hope that answers your question, but it would also be good if you can look it up and see exactly how a dialysis machine works - like whether a positive pressure is involved (generated by pumps etc) and what the dialysis fluid is made up of - it should give you a better idea.

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