KIDNEYS AND URINE - Creating Dilute Urine We consume fluid...

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Creating Dilute Urine We consume fluid that have way too much salt in them. We have to get rid of this salt. We also consume fluid that have too little salt (excess water). We have to get rid of excess water as well! This is when we make dilute urine This urine has to be more dilute in ions than the blood so it has to be less than 300 mOsm/L The short loop nephron is used to form dilute urine How do we create dilute urine? In the proximal convoluted tubule, solutes are reabsorbed and water follows them out of the tubule As we descend down the loop of Henle, the environment surrounding the tubule becomes saltier and saltier. As a result, more and more water is reabsorbed. The osmolarity is 900 mOsm/L at this point! This way above the 300 figure mentioned before. At the ascending loop of Henle, ion pumps place sodium and other ions into the surrounding environment The filtrate will become more and more dilute as a result The mOSm will fall as a result Strangeness in the tubules The ascending limb of the loop of Henle which used symporters to increase the amount of ions in the interstitial fluid. This works because ions came out and not water. Creating Concentrated Urine When we are dehydrated or when we consume a lot of salt in our food. If there is too little water or too many ions in the body, urine must be made which will reestablish the ionic balance This urine has to be more concentrated in ions than the blood to get rid of the extra ions so has to be more than 300 mOsm/L We can make urine that is about 1200 mOsm/L or about 4 times more concentrated than blood. The formation of concentrated urine occurs using a long-loop nephron. If the nephrons are lengthy, we can concentrate urine better!
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This note was uploaded on 01/16/2012 for the course KINESIOLOG 1Y03/1YY3 taught by Professor Parises during the Spring '11 term at McMaster University.

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KIDNEYS AND URINE - Creating Dilute Urine We consume fluid...

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